To install, follow the following steps:

1.) Take your ripped copy (clean ROM) of Golden Sun: The Lost Age and apply a patch via Lunar IPS.
2.) When patching choose either TLA_Anniversary.ips for the "normal" Anniversary experience or TLAA_noSummon.ips to do a challenge run where the ability to summon is completely removed (No Summon is NOT recommended for new or casual playthroughs)
3.) Once the ROM is patched, apply LeaderTheme_Overhaul.ips if you desire to play the game with the ability to change battle theme, based on who is currently leading your party.