How do you adjust the timing belt on a 1987 Plymouth Reliant 2.2 liter?

on 87 Plymouth reliant just above the crankshaft pully sligtly to the left theirs a head of a bolt that can be seen and u can loosen it but to adjust it the bottom plastic cover needs to come off and a little tool is put into a slot to put tension on the belt then retighten the bolt it works on a cam system its a round idler pully but the bolt is off center i been putting mine off because u have to get that bottom cover off that means all the belts basicly the whole front