To go from the airport to the city center (or conversely), two possibilities available to you : the aérobus T1 and T2 (express, with WIFI access) but more expensive than the "normal" bus, N 46.  To move you easily, you can take the subway (by taking a package of 10 itineraries or 2-3 days, "T Dìa", " T 10 " or the "Holà BCN" card). The first zone corresponds to all of the city.