Hak you have to ask a bomber pilot if he wants/needs a gunner.  If he says yes then in the radio bar you type .join <handle>  where <handle> = the pilots handle.
IE>  .join Rocket
NOTE:Once the mission is over and you are in the tower you must type .unjoin <handle> to get out of the plane.  otherwise you are stuck till on the ground again.  Isn't so bad if he takes another bomber but really sux if he flies a fighter.
Also after your 2 free weeks you will not be billed you must sign up for a paying account by submitting your credit card # or sending HTC a check/money order.  H2H is always free  
 
 S!
Rocket