(Project Catch 'Em All) Stage BGM Help Request

So, I recently downloaded some extra stages for Project Catch 'Em All. However, they come with no BGM music on their own and I am trying to add a few ones. In Project Catch 'Em All, the stage BGMs are set to loop, in order to make it feel like an actual Pokémon battle.

So, I have found some proper music for these stages, but I have no idea how to loop them at all. Long story short, could someone with enough experience in music editing please help me loop the BGMs I got for these stages?