including signature automatically

hi there, I've got a new macbook pro and want to know how I can make my signature appear automatically when I compose a new email. I've created the signature under preferences but still have to select it on the signature menu when I create a new email. Can anyone tell me how I can make it appear automatically? Thx so much, from Cape Town, South Africa

Under mail -> preferences -> signature.

Once there select your email account, then at the both change the choose signature to the one you want

thanks rman, it seems obvious now