I've always played that one player can attack a enemy in the combat phase but after reading 'Example: Tom exhausts Aragorn to attack a Hill Troll, and Kris exhausts Legolas to participate in the attack....' in the FAQ (page 3) I think I've been playing it wrong.

So if I exhaust to attack an enemy, another player can participate in the attack?

Another player can participate in the attack with any characters they have ready with the Ranged keyword. Most characters can only attack enemies engaged with their controlling player.

Thanks!

My mistake, after rereading this in the FAQ, it's very clear