well first you're gonna need to prove that you beat terraria 1. to do this you will need to beat terraria 1. done? good.
after that go to steam and launch tModloader
then download the calamity mod
calamity is the key to terraia 2.

so you got calamity, good! now you have to beat it without taking damage, go on. do it. we're waiting.

you're back? good. how was it? let's get back to business, terraria 2. oh btw you're gonna need to do terminus no hit. so now... finally, you'll be able to launch terria 2. go to steam and then store. once you've done that, search for "valve index vr kit" yes, you will need to spend over 1000 dollars, but it's worth it. Buy the vr set and then wait for it to arrive. when you get it, input your steam friend code into the store page and terraria 2 will pop up

CONGRATS! YOU NOW HAVE TERRARIA 2!

the game is very similar to terraria 1, so just play as normally, but when you beat the moon lord, you must have 20 of each fragment, and must craft the "final gamer challenge" which will let you fight the final boss. spoiler: It is moon lord 2. good luck