All you need to get started is a step ladder a 7 16 inch wrench and a flat head screwdriver.
Tighten garage door belt.
But basically assuming the belt is attached with enough slack removed the tensioner bolt should be able to taske up the rest of the slack once tightened.
In most cases all you have to do is adjust the opener belt of the belt drive tightening it to ensure smooth running.
The manual does not indicate how to solve this problem.
The only thing you need to do with a belt driven opener is to adjust the belt occasionally.
The specific procedure should be in the manual for your unit.
1 close the garage door.
Step 1 closing the garage door before beginning use the garage door opener to close the door and fasten it.
Tighten the adjuster three full turns clockwise to add tension if the door closed and did not remain open halfway.
Loosen the adjuster three turns counterclockwise if the door raised without.