how to edit a factions religion

[dinner]

Any advice on how to edit a factions religion would be appreciated.

I am a total empire modding nub.

[Veliky Kaiser Theos]

I haven't done that before, but I recall Britain's religion being protestant in the grand campaign, and non-conformist in the late campaign, so try editing startpos.esf.

[Agamemnon]

This is an old question, but in startpos.esf in campaign_env, if you go down to world, then find faction array you get a list of all factions. Pick the one you want to change, another box will appear. click it, and eventually it'll say "rel_(catholic, protestant, etc.)". Change that to the new religion.