This is very likely the first trophy you obtain.
A few levels in, other ships start driving along the levels, which you must pass. Often, while seeing these ships there will be purple icons on the track. drive through these and you can steal credits from all ships that you pass. You will only steal credits from ships that are on the tracks directly to the left and right of you, you won't steal credits from ships that are two lanes removed.
This trophy unlocked for me before I was halfway through the game, so you shouldn't worry about unlocking it. Just play through all levels and use the purple powerup icons whenever you see them.