download Lunar IPS.
download the rom (usually its fire red) [try dashroms on google, very good gba rom site]
download the .ips file.
open Lunar IPS, click on apply IPS patch.
select the good .ips file, then click ok.
select the fire red (or whatever the hack is for) rom file and it should say something like successfully patched.
then just open the .gba file with an emulator and done.