Another easy achievement available right after the prologue.
The bank in question is on the first island, and marked clearly on the in game map. It's fairly central, near the donut shop. The map key is on the left of the screen.
Approach the bank from the front entrance, and drive around the left hand side of it. Now drive out to the rear left edge of the bank's carpark, and on the grass verge ahead you'll see a stunt jump, fashioned out of corrugated steel.
Get a good run up from over the street, and drive off the ramp aiming for the bank. If you land on the roof, gently back off it and your achievement will unlock!
If you clear the bank, then you've added another successful stunt jump, going towards:
I recommend a car with decent acceleration, such as the Armadillo buggy you can find parked opposite Dwayne's scrapyard office.