Starting multi-boxing, only 2 accounts.

So my RaF partner recently quit on me, he gave me his account and the sub doesn't run out till october, so i thought i'll make the most of it. How can i go about controlling 2 characters at once on one computer for WoW. (My PC Can easily run 4 WoW's on good quality so no worries their. Thank you for any help you can give me :). (I'm not looking to spend any money this being a 1 month project). So just something simple should tide me over.

~Thank you :).

if the account is not in your name you cannot legaly multibox with it. Please purchase another in your name on your bnet account

It is my name, i even paid for it to get my friend to play, so any tips?

The sticky right at the top of this forum.