A willing creature at least one size larger than you with appropriate anatomy can serve as a mount.
Mounting or dismounting costs movement equal to half your speed. You can do it once during your move.
While mounted, you can control the mount or allow it to act independently. Intelligent creatures always act independently.
If the mount is knocked prone, you can use your reaction to dismount and land on your feet. Otherwise you fall prone within 5 ft.
If an effect moves your mount against its will, you must succeed on a DC 10 DEX save or fall off, landing prone.