Alright, first off get the 100% complete game saves here http://www.gamefaqs.com/console/psx/ Just click on the game you want, go to Gamesaves and then download the one you want. (it should be a .GME format)
Now Launch PSXeven.
Go to Memcard
Then Press Import, and add your Gamesave.gme
You can now close PSXeven
Now you have to find your game id. So launch your game from your psp. (make sure cwcheatpops.prx is activated)
Now hold select until cwcheat comes up.
Now go to "Manage Memory Cards" then "Load memory card 1 from memory stick"
For Crash Bandicoot 3, It should say "Currently selected memory card file: SCUS_94244-0.mcr
Last Operation: Open error
Now take what ever the game id was. And rename the memory card that PSXeven saved.
So for crash it would be: SCUS_94244-0.mcr
Now place the memory card in msroot\seplugins\cwcheat\mc
And the next time you load memory card 1 from cwcheat, it should say "Last Operation : OK!!"
Now in the game itself, press Load in the title screen, and you will see you 100% complete game save. Yay!!