Vault of time

How do I complete the first challenge. What I'm supposed to do? I have mage and tanks at level 4 support at level 3 warrior at level 2 and ranger at level 1. I'm supposed to upgrade all of them at level 3 or what?

How do I complete the first challenge. What I'm supposed to do? I have mage and tanks at level 4 support at level 3 warrior at level 2 and ranger at level 1. I'm supposed to upgrade all of them at level 3 or what?