To tame, you will have to hunt Ceratos and gather their venom spines. At level 75, you can learn to craft the Hemogoblin Cocktail. This is a special concoction you feed to your tamed dinos that will attract Ceratosaurus. When a Ceratosaurus attacks the cocktailed creature, they will slowly become blood drunk. When fully blood drunk, you can safely passive feed them. Higher level Ceratos will take longer to get drunk, and take more feeds to tame. Try to avoid using traps as a trapped cerato will deaggro fairly often. However, it often starts fleeing from your tank tame even when not trapped though; it's recommended to tame high levels using a Rhynio-carrying one as it starts to run away will instantly cause it to re-aggro. This is extremely important as a cerato will "sober up" very quickly if its not constantly chewing your intoxicated tank tame. You'll need about 2 cocktails per drunk cycle (remote use one at 50%+) and on x1 taming it'll likely sober up again before fully tamed (bring at least 4 cocktails on base settings if kibble taming a high level). Archelon are a really good tank tame candidate-just drop one in front of the cerato (without mounting it) and remote use the cocktails from the back.

Passive: You need to tame it while the Ceratosaurus is awake.