Only done a 16v golf before so presume the basics are the same.
With the belt off you must make sure the bottom mark is lined up and the top mark also,be carfull when tightening the cam belt tensioner up as the bottom pully can move a tooth ,once your happy that both top and bottom marks are lined up and the belt is to its correct tension, attach a spanner to the bottom pully and give it at least 1 complete turn before you attemt to start it making sure its free and doesnt jam .