To feed your Soul Puppets, simply go to "Camp>Creatures" and select on the right.
EXP meals can be bought from Item Shops such as Peddler's, but make sure your creatures are the proper level to eat them as there are minimum and maximum level limits for each meal.
Until the feeding timer expires creatures cannot eat again.
The length of this timer is variable and determined by the level of the creature after eating the EXP meal. However, it is also exponential, so expect a significantly longer wait for a level 90 creature compared to a level 70.
Please note that Rebirthing creatures will reset their feeding timer.
The Credit Shop Key Item Feeding Bowl will allow you to choose to automatically feed a creature a food item every 30 minutes for as long as it can.
Please note that all the usual restrictions still apply, such as, but not limited to, level limitations various foods have and whether or not a creature's feeding timer has expired.
Warning: Auto-feeding will not increase your "total creatures fed" score.
Though not as useful as Auto-Feeding, the Support Status perk Quick Feeding can make it easier for you to feed your creatures a default snack while you are on a mobile device and utilizing the Mobile Quick Actions menu.
Please note that neither Quick-Feeding or Auto-Feeding will earn you Player Experience.