I know I've seen this somewhere before, but now I can't find it. How do I change my team name and my logo and stuff? (Especially because I'm not a Star Wars geek!)

can only do it in offseason all the way up to training camp sim

First, it must be a custom league.

Second, you need at least 6 credits. I'm not sure of the actual cost.

Third, I believe it must be before preseason starts.

.... Someone correct me if I'm wrong, but I'm pretty sure those are right.

certain customizations are cheaper than others as far as credits. You can't customize after training camp