Hiya!
If you press the "U" command - it should bring up the Strongholds that you own and also Guild Strongholds / Guild Ships (if applicable). Any strongholds that you have purchased or had unlocked should be visible there. (its also the button up top that looks like 2 Farm Silo's) - Otherwise there is a spot on the Fleet that you can see all Strongholds too.
Just to let you know - for the Nar Shadda Stronghold - that was August 19th, 2014 (last year). So if you were subbed then, you should have it free - I did find
You should probably have it unlocked. If you don't see it I would petition Bioware to have them fix it.
Cheers!