lt1s10

Did you take the alternator off the head to access the bolts of the water pump? And now you need to put it on again? Or you just need to reinstall the belt? If you need a picture of the belt routing then you can go to the autozone website. There's a repair info link on the left side that'll have the belt routing.

If it's just the belt the tensioner is right on top in the center. Set the belt up on all the pulleys except for the alternator pulley. Then either put a box end wrench, a breaker bar, or a long ratchet on the tensioner bolt and release the tension on the belt while you slip the belt onto the alternator pulley. You can do it by yourself but if it's your first time either go slow so you don't slip and hurt yourself or break something or have someone else release the tensioner while you slip the belt over the pulley. Watch out on the first startup too just in case something is misaligned. The belt may fly off.

If you need pictures of where the bolts and the brace go on the alternator let me know and I'll snap some for you. But that should be pretty straightforward since all the bolts are different sizes and will only really fit where they belong.

edit: Just re-read your post slower. I guess you could slip the alternator pulley under the belt and wedge the alternator into position in it's bracket without releasing the tensioner but that's harder then releasing the tensioner and reinstalling the belt once the alternator is bolted down. And I think doing it that way you have more of a chance of damaging the alternator bearings or pulley.