Since the tub weighs north of 250 pounds, it isn't going anywhere! You need to install a ledger board on the back side. Then typically some large head roof nails just above the flange. I prefer a SS screw with a SS fender washer.
Depending on what access you have , you may need to have the drain shoe in place before you set the tub. This requires careful measurements.
So check with the plumber before you set the tub. Try to avoid having to muscle that tub in and out too many times!