Pro tip: Don't use explosive weaponry and really bad rexes with no saddles like the devs did. Fab Snipers for taming it with little/no collateral damage, actually decent rexes + imprint + saddles to kill it
Has to be summoned from a terminal in the snow cave. Entrance is just outside the northwestern part of the snow dome, near a river. Be prepared for a fight, as the cave is chock full of bears, yet is, and other high level dangers
You can tame the Ice Titan by shooting it's corrupted spots on it's body. Keep on doing this for a while until it falls down. After it has fell, walk up to it and claim it. (A claim option will appear like when you imprint on a baby.) I reccommend a good AR for this and some friends help. Solo isn't possible. Happy taming!