ok first, is nitepr activated?? first u need to activate nitepr by turing of ur psp and turn it on holding R if done right a screen should appear. goto plugins and activate it. next exit the recovery screen and itll take u to the psp mainscreen strt your game and wait for a little text box to show up in the top let corner, press HOME 2 time and hold the + and - sign and the nitepr screen should pop up then activate ur codes by pressing X and exit out of the nitepr screen, then press the musical note to activate it.

Im not a pro at this but this is how i did it.
P.S. u first have to have a txt doc. in ur seeplugins folder of the game's ID number (The number is on the side of the box) or something. EXAMPLE Sfdms game ID is UCUS-98641 so mk a txt doc of the gms ID number and put ur codes in that. Hope this helps...