At 5 months, much will depend on the puppies previous life. If it was living somewhere that it could withdraw to relieve itself, it may only take a day or 2 to establish communications. If it was shut up in a small space and forced to live in its filth, it may have lost its instinct for staying clean. Housebreaking will then be a long, hard process.
I am going to post what has worked for me for 15 little puppies since 1991 and for many other people I know doing about the same. A couple of points about your situation. A rack or grid in the crate will be a big help. Once it introduces him to a chance to stay clean and dry, he could decide he likes it. It also makes life much easier for you for what could be a long, difficult time. The ones designed for crates are expensive hard to find, and may not keep a Pom up high enough to stay dry. The closet shelving I used for many puppies fell apart a year ago. For my now 12 week old Holly, I went to big Lots and bought a food storage bin and drilled it full of holes. Holly was an exceptionally easy to housebreak puppy. She only had a couple of puddles in her crate and no bowel movements.
The timing is much longer for a 5 month old, making it tougher. With a 7 week old, you take it out just after it eats, and it will relieve itself within a few minutes. A 5 month old might go an hour. You will really need to learn to read the signs he needs to go and his schedule. That also means having your eye on him constantly. If he is used to fouling his living area any time he has to go, he will not adapt to a schedule you try to set. So read through my material and apply it to your older puppy.
Much of housebreaking is not training the puppy, but making it easier for your
Puppy, you, and your carpet while its body to catches up to its instincts. At
Around 8 weeks when the puppy goes to its new home, the time from when it
Realizes it has to go, and when it can't wait any longer is a matter of
Seconds. Only time will fix that. You can hardly be expected to be attentive
Enough to avoid all accidents There is no sense punishing the puppy for your
Inattention. It is not fair to punish you either, but you still have to clean
It up if you didn't have the puppy outside in time.
Housebreaking starts before you get home with the new puppy. If you don't have
A crate, buy one. I prefer the more enclosed, den like plastic ones. Skip the
Bedding. At first it gets wet, and later it can be chewed into choking
Hazards. A wire rack in the bottom will help keep the puppy up out of
Accidents at first. They are available with the crates, but a piece of closely
Spaced wire closet shelving from a home supply place is cheaper. If you
Already have a metal crate, covering it may help. Just make sure you use
Something the puppy can't pull in and chew. Dogs that start in crates as
Little puppies, accept them very well. Never leave an unattended puppy loose
In the house. If nobody can watch it, put it in the crate. I suggest letting
The dog have its crate all its life.
Choose a command and spot you want it to use. The less accessible to strays,
The less chance of serious disease. If it is a female, choosing a
Non grassy spot will avoid brown spots later. When you bring it home, take it
To the spot and give it the command in a firm, but friendly voice. Keep
Repeating the command and let the puppy sniff around. If it does anything,
Praise it. Really let it know what a good dog it is and how much you love it,
And maybe a treat. Note, being out there not only means you can praise it,
But it also keeps it from being snatched by a hawk. If it doesn't go, take it
Inside and give it a drink and any meals scheduled. A young puppy will need to
Go out immediately afterward. Go to the spot and follow the above routine.
Praising it if it goes is extremely important. If it doesn't go, take it back
Inside and put it in its crate and try again soon. Do not let it loose in the
House until it does go.
At first it is your responsibility to know and take the puppy out when it
Needs to go. It needs to go out the first thing in the morning, after eating,
Drinking, and sleeping. If it quits playing, and starts running around
Sniffing, it is looking for a place to go. Take it out quickly. You will just
Have to be what I call puppy broke until it is a little older.
By the time most dogs are about 3 months old, they have figured out that if
They go to the door and stand, you will let them out. The praise slowly shifts
To going to the door. Some people hang a bell there for the dog to paw. If
Your dog doesn't figure this out, try praising it and putting it out if it
Even gets near the door. A stern "Bad dog!" is all the punishment that is
Effective, and only when you catch it in the act and are sure you didn't miss
It going to the door. Clean up accidents promptly. I mostly keep the little
Puppies out of the carpeted rooms. Still I need the can of carpet foam
Sometimes. First blot up all the urine you can with a dry towel. Keep moving
It and stepping on it until a fresh area stays dry. A couple big putty knives
Work well on bowel movements. Just slide one under it while holding it with
The other. This gets it up with a minimum of pushing it down into the carpet.
This works with even relatively soft ones, vomit, dirt from over turned house
Plants, or anything else from solids to thick liquids. Finish up with a good
Shot of carpet foam. Note, do not let the puppy lick up the carpet foam.
Once the dog is reliably housebroken, your carpet may need a good steam cleaning.
Many people strongly strongly push cleaning up all evidence of past accidents. I am slower to suggest that. Dogs will return to the same spot if they can find it. When you see one sniffing the spot, that is your clue to run it out.
Oh, by the way, I looked at that www.ddfi.org
website. The housebreaking PDF didn't load for me. Likely no big deal since the web is full of bad advice. I have looked at dozens of others, and nearly all of them leave at least one important detail out. With all the bad advice around, no wonder I see so many people struggling for help with housebreaking.