These are like any passive tame as far as the action goes. Put the highest quality best taming food in your last slot and when close enough feed it

Now to get close enough to feed, you do need full grille and to be crouched and walk up behind it will let you get close enough.

Be prepared as it does jump/runaway after each feed, this is normal just track it back down and repeat.

It can jump into trees and cliff sides and 100s of meters away so be prepared to follow and kill other Dino’s it may get near.