When you locate the lever, pull upward until you hear a small pop. This is the sound of the catch on the Ascent’s fuel door release letting go. When you get out of your car, you’ll see that the fuel door on your dad’s car has popped open.
From there, you can simply swing the door open and unscrew the lid to the gas cap. If you’re unable to do this, try unlocking your car before repeating the process. If the gas tank still doesn’t open, there may be an issue with the fuel door release. In this instance, you’ll need to talk to a mechanic.