I am assuming that you took the lock-down bar off, removed the glass, and then lifted the playfield. Bally Williams playfields all kind of slide out a bit before you lift them up. Some also have a bar you raise to hold the playfield up. I am assuming you did not raise a bar (it's about 3 feet long and would be on the right) so we'll skip that and assume that the playfield is resting on the front of the machine, and that all wires are still attached. Sometimes the playfields need a little help to get over the hump and back on track. If you were to stand on the right hand of the machine, I am assuming there is some space on your right where you could reach behind and pull up on the back of the playfield. What you want to do is lift the back of the playfield (in your right hand) and the front (in your left hand) and lift the playfield an inch or two "over the hump" as you pull it to the right and set it back down in it's track. From here the playfield should easily slide into the back, and there should be two small metal hooks about 1 inch wide you have to fit securely back into the lockdown bar. If this doesn't work and/or doesn't describe your issue, please attach a picture for us.