If the sneakers are for the original, Hiro 3-based, Hiro Toon figure then the best way is to parent them. If the left and right feet are separate that's pretty simple - move each into position and parent it (from the Figure menu) to the appropriate foot. If the shoes comes as a pair, then it may be simplest to load two copies, hide the left foot in one and the right foot in the other and then proceed as above.