you have o pull off the oil pan, remove the rod caps, remove the head, rehone the cylinder to remove the glazing and give it a nice crosshatch. If its badly damaged and scored that motor is going to have to come out and get bored over. If not, after the hone, inspect the piston is its good, then you can go ahead and gap the rings and slap new rings on, orientating the gaps 120* apart. But usually if all other cylinder register good compression and one is bad, its due to some serious damage and not ring wear. Its from blowing a hole through the piston, blowing the rings and ring lands (new piston). Or it could be a valve. hope its a valve, thats easier. Pull that head and hope youve been a good boy this year. Merry Christmas.