very easy:
1)Copy vcscheatdevice371.prx from GTA VCS cheat device download to X:\seplugins (create the folder if nessesary)
2)Add the line "ms0:/seplugins/vcscheatdevice371.prx" (without the quotes) to game.txt in X:\seplugins (create the file if nessesary)
3) Copy topcheats.txt to X:\cheats\vcs (create the folders if nessesary)
4)Go to recovery menu (Turn ur PSP off and turn it on again while holding down R) and go into Advanced->Advanced Configuration and make sure "Plain Modules in UMD/ISO" is enabled and also go into Plugins and enable vcscheatdevice371.prx
5) Fire up GTA VCS UMD or ISO and enjoy the cheat device
Tested on 3.71 M33-*, 3.80 M33-* and 3.90 M33-*
Download (v2.4)