If all you want to do is get the ball to the goal, just slide things around and see what happens. However, if you're aiming to solve this puzzle in as few moves as possible, you'll have to think ahead. Remember that moving one block immobilizes others.

Only blue blocks can move at the beginning. Slide the one on the right up, and then arrange the two purple blocks underneath it in a horizontal line.
Next, move the lower yellow block over to the right. This will give you some space to work with on the left.

If you've followed the previous hint, you should start to see the answer to the puzzle.

In order to move the yellow block that's directly beneath the ball, you're going to have to move that green block on the left. To do that, go ahead and move the bothersome blue block out of the way.