Very easy, simple achievement. Go into customize, then 'profile and select 'Edit your Profile Team'. From here, just select your most used characters and register them, this makes selecting your favourite/most used characters faster by selecting 'use profile team' at the start of matches.
Next, select 'Customize Icon', and choose any icon that takes your liking, doesn't matter which one.
Finally, select 'Customize Message' and select one from the list. Also, selecting 'No message' also counts if you'd prefer not to have one. The achievement will pop as soon as the last step of this is complete. Easy 10G.