This achievement can be obtained naturally by simply roaming the open world, (look for brown plank ramps that curve slightly upward and drive off them, it does not matter how long you stay in the air). However, it is also possible to get the achievement over the course of the main story, very early on, if you simply stick with it long enough.
Play through the main missions in Chumbucket's stronghold, The Tabernacle, until you fulfill his request to get the car nitrous. After you achieve this, he will request you demonstrate the nitrous by taking the car off of one such jump. Once you do so, which you must to advance the story, achievement unlocked.