Well start with dungeons. Learn the basics of holding aggro. Typically this is going to involve using your AOE enmity generator a few times, perhaps following with the single target one and when the mobs and comfortably locked down, you can then go all out on DPS.

Then do some extreme trials, so you can learn about tankswapping and having a cooldown plan for tankbusters and such.

There's a number of indepth youtube tutorials for each tank class if you'd like to study more.