While I don’t have this exact model, on the ones I do have there is generally a slotted head screw that you turn to adjust the tension on the blade. (You may have to loosen a nut while you make the adjustment then retighten it to lock it in place)
Post pictures of your actual unit with both sides of the casing visible and I’ll see if I can help you out.
I think that black knob on the side?
@troy That appears to be the oil fill cap.
I don’t have any idea right meow but I believe the item in context is this:
While I don’t have this exact model, on the ones I do have there is generally a slotted head screw that you turn to adjust the tension on the blade. (You may have to loosen a nut while you make the adjustment then retighten it to lock it in place)
Post pictures of your actual unit with both sides of the casing visible and I’ll see if I can help you out.