First of all, keep in mind that this is NOT a knockout tame, you need to put one of its taming foods in your last item slot (berries are the easiest, and I’m pretty sure mejoberries are it’s preferred berry) then, you slowly walk up to it from behind and feed it, as its eating the food, you will get the option to mount it. Once you are riding it, feed it every time it stops running around and tries to buck you off, repeat this over and over until it’s finally tamed. Also, try not to mess up and get bucked off, because the taming percentage will drop at light speed as soon as you do.
Also, before you start taming it in the middle of nowhere, I recommend that you first grab it with a flyer like an argentavis, then drop it in a Dino gate enclosure, If you don’t trap it, it’ll most likely take you on a trip over to the nearest raptor pack. After you trap it, you may need to leave it alone for a few minutes until it finally calms down, then tame away to your hearts content, Hope this helps! :)