When you use a glider it will be equipped to your trade pack slot, the slot that is used for any equipment that goes on your back. If you open your character window by pressing 'C' you will find the equipment slot in the bottom right, below your Lute.

There is also a quest around level 5 for Firran players called Fleeing Whisperwind which provides a temporary glider. Once you land, you will no longer have access to this glider.