Fundamentally, tanking is very simple.

For trash, you're just going to be using your AoE enmity move a few times to get everything glued to you then either do your single-target rotation or AoE spam everything down. Cooldowns should popped on a rotation to ease healing or as an emergency if you're about to die.

For bosses, you're going to mostly be respecting the same mechanics as everyone else, but need to pay attention to when tank busters are coming and pop your mitigation cooldowns to avoid being one-shot or killed by the auto-attack that tends to follow shortly after. In raids, there's generally either a debuff that forces tank swaps or an add the off-tank needs to grab and position for a quick takedown.

As a general rule of thumb, you never want to be facing enemies towards people or standing near them due to a lot of them having AoEs telegraphed and otherwise that will be targeted on you/aimed in your direction.