you only need to be level 30, but you must be logged on to DR client, not just have it on your acct.
As someone said, you must go to your guild head, which is a relatively new NPC for each guild. If you talk to one of your class trainers, they will point you to the NPC's name you need to see.
This guild head will give you a note (and offer you to start your epic quests also) which will give you access to the King's chamber instance.