In both the Asmodian and Elyos town in the Abyss you can find Teleporter's. These Teleporter's can take you to almost anywhere in the Upper and Lower Abyss. If your faction has any captured Forts this Teleporter can take you there. Also in addition he/she can take you to the Eastern and Western Shards of Latesran.
In order to Teleport to one of the Forts in The Abyss your faction will need to be in control of it. If you don't have control of the Fort then it will be greyed out (Like every area in The Upper Abyss is). Also the ONLY place you can find Teleporter's in The Abyss is at each factions town. Once you teleport to an area such as a Fort or a Shard there is no way for you to get back except for run yourself.