It's a female cocker spaniel which is 5 months old and often does her business inside

The best way to train any puppy is encourage them to go at first on paper in the kitchen, or any where they are go basically that will be easily cleaned if they make a mess. Moving the paper every so often closer to the outside door. When you have trained them to do their business on the paper at the door you are ready to start taking them outside always go with them when you realise they need out they will not always cry at first this sometimes comes later once they know to alert you. The most important thing to remember is always always praise your puppy when they have managed to do their business once you have achieved this they will be happy that you are happy and will want to go out but it does take a long time for the puppies spincter muscle to tighten so never ever be tempted to scold your puppy if he/she has an accident as this is counter productive as they will read your body languge different to how you want them to interpt it and thing they have done a good thing. So only make a fuss of them when they do their toilet and they will learn much quicker. Lastly but most importanly give them a "trigger word" for example toilet so when you take them outside say now you do your toilet like a good girl and afterwards praise them.
Hope this is helpful goodluck with the puppy training!

Praise is SO important, as mentioned above! To really get the potty training aspect down, it is important that you are home and able to stick with a routine your pup can follow. To start, take her outside every two hours or so, and only use trigger words such as "go potty" or "get busy" (use the same words every single time as consistency is key). When taking her out, make sure you take her to the same spot each time, so she really gets used to going outside. Once she does her business, reward her with praise and a treat!

Once you notice that no potty accidents are happening in the house, you can increase the time increments. Instead of letting her out every 2 hours, you can bump it up to every 3 or 4 hours.

Once trained, or on the road to being trained, many dogs will alert you when they have to relieve themselves, so you can let them out. If you'd like, though, you can teach her how to ring bells to go out. They can be a great bridge to the communication gap, and a great sensory item for conveying necessities! You can order these bells anywhere, just search "potty bells", and the instructions are included in the package.

Good luck! I hope this helps! (: