If the adjustment needed is small you can get on your knees and give a swift tug on the base of the door in a skyward direction. After all, the reverse is how it started sagging to begin with. If more is needed then you can loosen the hinge bolts under the fascia just forward of the door. Be careful not to loosen all of them completely or you will be playing with this the rest of the day. Slide the hinge by leaving the lower bolt semi-tight. Best of luck.