Creating Custom Abilities Help?

[Valkyrie of the Rising Sun]

I'm trying to implement a few custom abilities which will trigger weather conditions (e.g. Hail) and terrain (namely Electric Terrain) respectively for rejuv v13.5, but I'm not sure where to go aside from abiltext.rb and Battle_Move.rb which has the code for abilities which trigger the weather/terrain on entry. Can anyone help me?