Dark Souls games all have an optional system where you can turn into a dragon. I was disappointed to see it missing from Elden Ring, but that's no longer the case: Shadow of the Erdtree adds two different Dragon Forms to Elden Ring, so here's how to unlock them.
Elden Ring DLC: Shadow of the Erdtree – How to Unlock Dragon Forms
To access the items that grant you Dragon Form in Elden Ring: Shadow of the Erdtree, you'll need to clear the Dragon's Pit dungeon. This is an optional side-dungeon in the eastern Gravesite Plain, near the Suppressing Pillar. If you're unsure where Dragon's Pit is, approach the giant pillar in Gravesite Plain and explore the land formations slightly northwest until you find a cave entrance.
After defeating the Dragon's Pit boss and exiting, you'll come to a crossroads. You can either go northwest to Jagged Peak or south to the Grand Altar of Dragon Communion. Take the road south until you reach the petrified remains of the giant dragon hanging over the Cerulean Coast.
Ride to the dragon and at the base of its remains you will find a giant burning crucible, a Site of Grace and an NPC: the Dragon Priestess. Talk to her until she gives you the option to devour draconic essence, which you should accept.