If the green locking tabs are hard to turn, turn the bedknife adjustment knobs towards the “-” on the bedknife. Once these are backed off from the “+” the green tabs should move freely. Insert the green tabs into the frame of the machine but do not lock them down yet. Ensure that the lobes on the bedknife are pointed downwards and it should fit right into the machine. Lock down the green tabs and you are ready to use the machine.