Second wow Account won't attack

Hi there, just started another char on Wow with the Isboxer. Just got a little issue.

My main account is casting a spell and my second char do the same.

But when I switch to the second char ( i mean when he is in the main window, the bigger one ) I cast a spell with this one but my main char doesn't do anything.

I can of saw that he won't auto target my target.

What should i do to correct this!!!

Thank you in advance!!!!

[lax]

Follow the WoW Quicker Start Guide part 3 and later, the issue you're having should be covered