Note: This requires you to start a new game. there might be a way of changing it without having to restart but i don't know how.
step 1. Open your Editor and load your database.
step 2. select Competitions and search "European Champions Cup" (ID:1301394)
step 3. Simply change the Name to "UFEA Champions League". I changed the short name to 'Champions Leauge' and thre letter name to 'ECL' but that's optional.
When you start your game, You will have to enable the editor data. You will find that in the new game screen when you are selecting playable leagues.