To get this achievement go to the basketball court in the Detroit city streets, just behind the Downtown Apartments. Locate the basketball court here:
Near the hoop should be a basketball, which you should be able to pick up with the Interact button. Now, you need to score a basket by getting the ball through the hoop. Sounds simple, but trying to get this by throwing the ball can be tricky.
The way I did this was using the 3 green barrels to the right of the hoop. I stacked these so that two of the barrels were at the bottom just in front of the hoop, and then one more balanced on the middle of those two. I then jumped on one of the bottom barrels, then onto the top barrel using them like steps (with the ball, obviously) then I just literally dropped the ball through the hoop by pressing X, and the achievement popped.
This was after about two dozen tries by getting it in by throwing it. But I think the margin for error doing it this way is so small, you're much better off just dropping it in from above. If not quite so badass.