For this achievement, you'll have to complete five of the ten treasure chest chases in Rayman Origins. There's one in each world, and for you to be able to do the chases you need a certain amount of Electoons (the smiley things you rescue from the cages in every level). The fifth one needs 100 Electoons to open and is in Mystical Pique. Once you have enough Electoons for a chase, the game will notify you about it.
As for the chases, you'll need to sprint (RT), jump, swim and fly through a level while chasing a treasure chest. These levels are not particularly hard, but some will test your patience. If you die, just try to remember how and where you died so you won't die there again.
A tip for the swimming parts: Sprinting is faster in water too. But if you sprint and then press b repeatedly, you'll go even faster. Try it!
Here is a video of all the chases in Rayman Origins. It was NOT made by me and all credits go to TheStrawhatNo for making it.