There creatures are almost entirely passive, so long as you don't attack them. If you do aggro one (to kill it for either it's great pelt supplies or it's horn), it is best to get on top of a small cliff or something like that. Running away is almost always futile, as not only do they move faster the longer they charge at you, they do up to 10 times as much damage. If you are to run, don't run straight, unless you'd like to be a rhino's horn decoration.
to do the RAM attack all of you have to do is run and it will start to speed up like a dire bears and run into your enemies/creatures with your woolly rhino and when it the horn is near the enemies, TAP the ATTACK button and there you go it deal massive damage, i don't recommend doing that to a brontosaurus tho (sorry for my bad english)
They are everywhere in the snow mountains. A group of wolf or smilodons will aggro them and if the rhino is high level, you can tame it but don't forget the bad boys who want to eat it, protect it from the smilodons that served as tank for the tame.