If your flight arrives at Terminal (T1) at Barcelona Airport you will pass through the gates and passport control and find the relevant baggage reclaim by using the screens provided. If you are on a domestic flight arriving at Barcelona Airport you will go through the area called the Sky Centre (with no passport control) and find the baggage reclaim area.
Once you have located the reclain area at Barcelona Arrivals you will exit to La Plaza (the square). This is where you will meet anyone waiting for you are car hire representatives. Also here are the car hire desks and access to public transport and taxis.