Make sure you have room on your memory card for more than one save. The
idea behind the cheat is to import your own character into a map you
control. So, if you are after experience fight your way through the game
to a boss fight with an easily accessible save point. Fight the boss
down to the last hit and then withdraw to the save point. Save the game,
this will be the map reference. Now, go ahead and wander back towards
the boss and kill him. You gain the xp and loot of the boss fight.
Return to the save point and save your game on < Create New Save Game >.
This will create a new save that we'll use to import from. Now, exit the
game and reload your map reference save (1st save). Once inside your
game, hit start and go to Add/Remove Players... Highlight your own
character and hit triangle to import a character. Import your character
that already has the boss experience into the map reference save you
created and you now have the opportunity to kill the boss again (in one
blow no less) and regain his xp and loot.