10'000 steps riding a Chocobo is unlikely to come naturally in a normal playthrough, requiring you to grind it a bit, probably by rubberbanding your left stick so the choco runs in circles.
However, if you are aiming to collect all the fragments, you should leave this achievement until you've done that. With all the 160, you'll unlock the 'Clock Master' skill from Serendipity. This allows you to play the game at twice the speed, cutting your grind time in half.
Thanks to Worhammer and Zombie Deej for reminding that the achievement only unlocks when you dismount the Choco. So check regularly if it's done yet.