Handy feature: if you're attempting to move a mob that is within a withholding period, you'll receive a warning notification.
Mob moves are what drive the Days Grazed and Days Rested counters on each paddock, see here for more info.
Move a mob:
*When moving multiple mobs within a paddock you can also deselect mobs that are to stay behind.
See also how to split a mob, and how to merge mobs.