How do i make the leaders in my scenario all have a certain age outfit throughout ages.

Do you mean SGL/MGLs, or Leaderheads?

If you mean the leaderheads, you simply look in the editor under the "Civilizations" tab and select the one you want to change. The leaderhead section lets you enter two FLC animations for each era (one going forwards and one going backwards). Choose the ones from the era you like and copy and paste them into the other eras.

Thanks! I'll do that. Party on dudes.