In the Companion Menu on the top right side you want to visit the Collectibles section where you can assign costumes from the Appearance tab or mounts in the Mount tab.

  • Any appearance or mount that you unlocked on your own characters can be utilized for the Companion.
  • you can also change the outfit of a Companion at the Outfit Station.

Companion mounts and appearance Blackwood ESO

Here you can see an example of both the Player and the Companion being on a mount in Blackwood.

Player and Companion mounted Blackwood ESO