Alternator

So i got an alternator from Napa, took my old one out and pretty much put the new one in...The problem i'm having (i dont have a hayes manual or anything) is that i cant get the lower left hand screw in...it doesn't seem to line up well. Is there some sort of tensioner to loosen the slack on the belt? Theres that diaganol screw on the lower left hand side of the alternator under the power steering pump; is that a tensioner for the belt?
any help would be appreciated.

thanks


-Alex