EDIT: I couldn't get CoderPR to work on my PSP Go without it crashing, so for now PSP Go users will have to use NitePR. Basically the same thing, but some prefer CoderPR for other reasons.
Download CoderPR here: http://www.mediafire.com/?o8oe4z8zq9j448t
Download NitePR (For PSP Go) here: http://www.mediafire.com/?r0vp741n75i0kqd
Okay installation for CoderPR:
1. Select the "SLIM PSP VERSION" from the .zip and extract it somewhere, for instance the desktop.
2. Drag CodePR folder to the root of your memory stick.
3. On your memory stick, open your seplugins folder.
4. Now open your original game.txt file (make one if there isn't one)
and type without quotes "ms0:/coderPR/coderPR.prx 1"
NitePR (For PSP Go users)
1. Extract the NitePR folder into your seplugins folder.
2. Extract the nitepr.prx into seplugins.
3. In game.txt type without quotes "ef0:/seplugins/nitepr.prx 1"
4. Then save the text file.
Installation is now complete.
Now to install new codes do the following:
1. Create a new text file for the game you want inside the CoderPR > cheats folder on the root of your memory stick.
2. Name it by it's Game ID, for example Kingdom Hearts Birth By Sleep [USA] is ULUS-10505.
3. Open the new text file.
4. Obtain the cheats by google searching "Your game nitePR Codes". For example I would type, "ULUS-10505 NitePR" and it will give a crapload of results.
Though alternatively, you can sign-up on http://www.onehitgamer.com and simply search for your cheats there.
5. Paste over your cheats to the text file in the format like below. (You can also use the included text files for an example.)
;Kingdom Hearts Birth By Sleep
#Mirage Medals 
6. Then save it. Make sure you have the cheats for the correct region, for example my game is Kingdom Hearts Birth By Sleep [USA] so I used the Game ID for the United States version.
To open CoderPR in game do the following:
1. When you see the little bar on top of your screen that says to press "Home twice to enable" Do so.
2. Then press both Volume + and Volume - to open up the menu.
3. From there it's pretty self explanatory so have fun with your hacks!
If you thought this was helpful, please say thanks.
If you also have questions feel free to ask, but on this thread ONLY. Do not make any other threads because Mods will get annoyed. Thanks!
Do not use this program/homebrew to ruin the fun of others online.
I will not answer anybody who has questions about using these cheats online.