lol ^ title

What do I do ?

Buy it, Checkmark it in "Data Files" (PC) Buy it from xbl, look around until you find a Dawnguard or Volhiar base or hear rumors about it. XBOX
PS- Be more explanatory.

It might be somewhat helpful if you told us what problem you are having?

my Hud is gone, cant enter castle volkhir, Spells dont work, armor floats around my character

Umm, wow. What console? But my first advise delete it then reinstall.