DLC dungeon entrances are often located in base game zones, Rift and Stonefalls in this case. Port in if you do want to walk or do not own the zone where entrance is or just queue.
Myself learned yesterday that if you want to walk in veteran dungeon version open the Goup finder, activate Group and find the tiny icons where one can set the normal or veteran mode. Then walk in. (There is a large shield watermark on loadscreen for veteran version.)