Please find Teleport Master and visit Silithus Camp to get "Book of Powers" - Premium Item.
Once you find Teleport Master navigate to - Extra Portals -> Silithus Camp.
To use it, just start casting and move after very first second - Once menu with commands appear.
You can use Book to teleport to Dalaran after anytime you wanna - there is no cooldown.
Or check guide here -> https://shadowburn.net/blogs/features.php