Instructions
Start GameShark with "Pokemon FireRed" in its game slot. The cheat device will use the "Automatic Game Detection" to recognize "Pokemon FireRed" and show the available cheats.
Move the cursor with the D-pad until it is lined up next to "Add New Cheat." Press the "B" button. Designate a description for the cheat with the "A" button, "L" button, "R" button and the D-pad. Press "Start."
Use the on-screen keyboard to enter the "Have All Pokeballs" cheat of 420259D80001 0001000C0004 420259DA5212 0000000C0004. Press "Start" to confirm the changes.
Return to the cheat codes screen. Press "A" while the cursor is hovering over the name to activate the cheat. Press the "Start" button on the Game Boy Advance.
Select "Load Save File" on the main menu of "Pokemon FireRed." Your "Bag" should now have 99 Master Balls.