Do you mean the wild pokemon modifier that lets you choose what pokemon you wanna see and what level?
If it is, its pretty simple:
Make sure its turned on. (the ar code)
Go to your calculator and type the pokemon's pokedex number that you want to see. Press L.
Clear that on the calculator, and type in what level, press R.
Go into the grass...
and the pokemon should appear.
If not you got the wrong code.