The user group you are in, that is your rank. Let me explain them a bit more:
FNG: This one has nothing to do with the Arena itself. Once you have 20 as your post count, you'll instantly be promoted.
Soldier: Once you have 20 posts this is what you'll be promoted to. Now you'll have to work hard to be promoted to the next rank.
Commander: To be promoted to this rank, you have to earn 20 Hero Ribbons. Users in this rank will now be able to access more Arena game modes.
Prestige: To be promoted to this rank you must have earned 50 Hero Ribbons.
Prestige 2: To be promoted to this rank you must have earned 80 Hero Ribbons.
Prestige 3: To be promoted to this rank you must have earned 110 Hero Ribbons.
FNG: This one has nothing to do with the Arena itself. Once you have 20 as your post count, you'll instantly be promoted.
Soldier: Once you have 20 posts this is what you'll be promoted to. Now you'll have to work hard to be promoted to the next rank.
Commander: To be promoted to this rank, you have to earn 20 Hero Ribbons. Users in this rank will now be able to access more Arena game modes.
Prestige: To be promoted to this rank you must have earned 50 Hero Ribbons.
Prestige 2: To be promoted to this rank you must have earned 80 Hero Ribbons.
Prestige 3: To be promoted to this rank you must have earned 110 Hero Ribbons.
