how does one get to be able to use more heros in the arena?
I know that the question is how can one use more heros in the arena. Such as I'm battling people who have more heros what I can only use three. So in other words the question should be how can one use more than three heroes in the arena?
if you have 5 different heroes and the game doesn't let you use them then something is probably wrong
There may be a couple reasons:
1. Your "8" heroes, some of them may just be slimes... which cannot be used in battle.
2. You cannot use duplicate heroes. If you have 3 exe, 3 pain-da, 2 angel, you would only be able to use one of each resulting in 3.