We were in Barcelona last Sept. for a Med./WBTA B2B. As mmouse37 said, just follow the signs. We also had
DCL transfers which made it very easy and had a private car with DCL rep with us (wife & me) to hotel. Warning, the pickpockets are everywhere in that city, so be careful. Also, you have to see the Gaudi stuff...park, buildings and, of course, the cathedral. You need reservations for almost all of these attractions. Your hotel staff can help you get set up if you haven't already booked from home. Hope you have a couple of days planned to site-see and eat. Love the place!!