You can do the following (I guessed on table fields,etc)
SELECT s.studentname , s.studentid , s.studentdesc , h.hallname FROM students s INNER JOIN hallprefs hp on s.studentid = hp.studentid INNER JOIN halls h on hp.hallid = h.hallid
Based on your request for multiple halls you could do it this way. You just join on your Hall table multiple times for each room pref id:
SELECT s.StudentID , s.FName , s.LName , s.Gender , s.BirthDate , s.Email , r.HallPref1 , h1.hallName as Pref1HallName , r.HallPref2 , h2.hallName as Pref2HallName , r.HallPref3 , h3.hallName as Pref3HallName FROM dbo.StudentSignUp AS s INNER JOIN RoomSignUp.dbo.Incoming_Applications_Current AS r ON s.StudentID = r.StudentID INNER JOIN HallData.dbo.Halls AS h1 ON r.HallPref1 = h1.HallID INNER JOIN HallData.dbo.Halls AS h2 ON r.HallPref2 = h2.HallID INNER JOIN HallData.dbo.Halls AS h3 ON r.HallPref3 = h3.HallID