Make sure you have a pet selected on your profile so you're able to use items, then go to your inventory and use the potion. There should be a dropdown menu with the names or ID numbers of your dead pets.
If they've lost their names you'll have to go to the graveyard, found in Otroe Circle on Reiflem, in order to find out which pet belongs to which ID number so you're not stuck resurrecting random pets blindly. P:
Normal User
Normal User
