I'd recommend having at least 70 tranq arrows and a crossbow before you try and tame it.

1. Find a Bronto

2. Get to a high place

3. Shoot at head with tranq arrows(or tranq darts if your higher level) until it's knocked out

4.feed it lots of mejoberries

5. Give it good name

And you've got a Bronto CONGRATULATIONS 🎉🎉🎉!!