When it comes to DLC, FromSoftware likes to make it a bit of a challenge to actually find the new content. Dark Souls was notorious for how cryptic it was to get to its DLC, but thankfully*, Elden Ring* doesn't make things quite so hard.
Still, if you're preparing to play Shadow of the Erdtree and want to see the new zone, fight new bosses, and get new weapons right away, you probably don't want to spend hours scouring the massive map looking for the entrance. There are two steps you need to make sure you complete before you can access the Shadow of the Erdtree content, but after that, it's smooth sailing. Here's what you should complete in the base game before the DLC launches.
How to access the Shadow of the Erdtree DLC
FromSoftware let us know beforehand that there will be two mandatory bosses from the base game that you need to beat before you can enter the DLC. Both are technically optional to beating the main game, so there is a chance you might have skipped one or both even if you finished the story.
Step 1: Beat Radahn.
This is the set-piece boss of Caelid region most players will fight naturally while playing the game, but Radahn is technically skippable.
Step 2: Defeat Mog, Lord of Blood.
Of the two requirements, this one is by far the most challenging. The first hurdle is even finding Mohg, which requires you to reach the Mohgqyn Palace. You can do this by either following White Mask Varre's questline or finding the teleporter in the Consecrated Snowfield.
Once you reach this small underground zone, fight your way through and defeat Mohg.
Step 3: After Mohg is slain, you will be able to interact with the creepy giant egg at the back of his arena. Once you do, you will be whisked away into the Land of Shadow.