In case you missed it, running now through the end of the game week early Wednesday, Ulduar raid Timewalking is available.
To get started, join a raid group and head to Dalaran. In the middle of Dalaran, Vormu has a quest for you that rewards a Heroic raid level piece of gear and a hefty 500 Timewarped Badges. All of the usual bonus rewards are also in play, such as pets and mounts. And Vormu can also teleport you to Ulduar.
Then all you have to do is kill Yogg-Saron!