First of all, you have to copy the seplugins folder from "MS_ROOT_371" within the archive you have downloaded. This should then be put into the main directory of your psp memory stick.
So for example, your psp memory stick should look like this...
ISO, MP_ROOT, MUSIC, PICTURE, PSP,
SEPLUGINS, VIDEO.
Once you have it looking like that, boot up the recovery mode and when you go into the plugins, you should see the cheats plugins
