For some time now I have little water pressure in my kitchen and bathroom through just the hot water. Then just the other day I went to check my water heater and noticed that it was leaking through pressure valve so I put a bucket to catch the water. Since the water heater started leaking I have little hot water. How should I fix this myself?

Thank you!

You'll have to drain the water heater but first shut the power off at the breaker so you don't blow your elements if this is electric lift the relief valve when draining it then just replace the valve making sure to reconnect it to the piping

In some cases you can get away with cleaning a leaking pressure valve, but usually you have to replace it. Doing so will not improve your water pressure. Likely you have some crud in the lines. If you have a shut off to the water heater, close it, leaving the main on for the cold. Open the drain valve and put the bucket under it or run a hose to a drain. With the water draining, go to the kitchen and open both the hot and cold water. Hold you hand over the spout forcing the cold water back through the hot line. Shut it off and go do the same in the bath. With a little luck, that will flush the crud that was reducing your water pressure back to the hot water tank and out the drain.

Cleaning/replacing the relief valve likely won't last long unless you identify why it started leaking in the first place. One frequent cause is the back flow preventers now required in many places. When the tank fills with cold water, it expands as it heats. The excess has to go somewhere. Without a back flow preventer, it can just go back the cold line. With one, the solution is an expansion tank. They are just a small tank partly filled with air teed off the line before any valves.