How do I see how much BE my wolf has, what is BE, and how do I get BE?

BE = Battle Experience and can be found on your wolf's page:

Thanks Vennenum

Battle experience makes it so your wolf can get stronger attacks. Every animal the wolf kills is worth one BE. Every time you kill about 25 animals you should get another, stronger attack for that wolf. By increasing BE, your wolf will be better at PvP and killing stronger animals in explore. The strongest attack is Death Grip at about 925 BE. I've found the fastest way to get BE is using only one or two wolves in explore. Of course, if you find a powerful enemy, you can just go back to the explore menu and add more wolves to defeat that animal.

@Valiance