To start battling, simply click the Vs. button at the top of your screen. Then click where it says Arena. You will then automatically be put into a duel with another Moga team that will be around the levels of your own Moga team.
Couple Of Arena Tips
#1. Assorted Zodiac Signs: Make sure each Moga in your team has a different sign. This way you will be able to choose which Moga is strongest against your opponents Moga and make the switch.
#2. Rarer Mogas = Stronger Team: The PvP matchmaking system is solely based on the level of your Moga team so if you have Super Rare, Epic, Legendary or Galactic Mogas this will give you a definite edge in the Area.
Feel free to comment with any other tips you may have on the PvP arena.