When you load up the game after buying and downloading the DLC, you'll have a new side quest awaiting you. Set a waypoint and head there.
This will take you to the South Akkala Stable, where you'll find...
...Super Rumor Mill EX: Volume 2. It reads:
"Traysi here! No matter where I go, my love for rumors inevitably follows... Don't you make it a point to dig up rumors while traveling? In any case, today's topic of discussion is...The Dream of Teleportation! Apparently, there was once an ancient medallion that could instantly teleport you to wherever you placed it... What's more, this wondrous item may still be somewhere out there, just waiting to be scooped up! I must say, it sounds like the perfect item for travelers, adventurers, and rumor-lovers alike! I hear the treasure chest containing this tool is located beneath a labyrinth in northeast Akkala. Is it true, or just a beautiful dream? I'll let you decide that for yourself, dear reader."
If you've given Zelda's map a good going over, you'll be aware that there is, indeed, a labyrinth to the northeast of the map. In fact, you'll actually need to complete the Trial of the Labyrinth to get to the medallion, but thankfully we've already written a full guide on this. Check it out to make things easier on yourself.
You're heading not just into the heart of the labyrinth, but right next to the shrine in there. If you've beaten the Trial of the Labyrinth, you can warp right there.
Once you're there, there's a hole in the ground right in front of you with a jet of air coming through it. Drop through this to find...
...a proper Guardian graveyard. Or so it seems. Wander to the chest ahead of you and open it for a Diamond Circlet, and you'll start to see a few of the Guardians spring to life.
They're stationary, but there's a few of them - you could find yourself with three lasers aimed at you at once. The best way out of this is to run for cover behind the dead guardians, but remember that you can deflect their lasers back at them with a well-timed shield parry.
As always, turning on your magnesis power highlights movable objects, including the treasure chest the medallion is held in...
...but for easy reference, here's where you want to head on the map. It's on the far wall, so expect to have some lasers shot at you.
Grab the medallion, and then either stay and fight (if you're so inclined) or warp right out of there. The medallion is now yours!
By selecting the Travel Medallion from your inventory, you can now drop a single point anywhere on the map and then warp back to it whenever you want. It's very handy if you need to duck out while exploring Hyrule Castle, or if you find something cool but can't find a shrine nearby, or if you want to climb a mountain but need to go somewhere to wait out the rain or heal first.