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
Try to hit the coropted glowing things around his body. Ice you have destroyed all, it should fall down on the ground knocked out. You do not need any taming food for it, Just go up to it and click tame to tame it. No need to build a saddle because it already comes with one.
Use a Mek have like 50 Element on it. So you can fly and dodge attacks. Be careful the Titan can one shot or do a ton of damage to your mek. The way to tame it is you use a M.S.C.M. On your Mek with around 50 Cannon Shells. Make sure you are accurate and hit the corruption. Another Tip you can farm the Desert or This one (because they are the easiest to kill) To get Cannon Shells instead of crafting them.