L9 Sud Train to Barcelona Airport

Head to Universitat, Catalunya, or Urqinaona for L1 (Red) to Torrassa then change to L9 (Orange) for Aeroport. Aerobus may be more convenient.

I think David's onto something. With the Aerobus there would be no stairs to negotiate. Service is frequent. You'll need to know whether you're heading to Terminal 1 or Terminal 2, because there are often separate buses. There's a ticket-vending machine right by the bus stop, which is near El Corte Ingles.

https://www.barcelona-tourist-guide.com/en/faq/airport/transport/metro/metro-to-barcelona-airport.html

agree to catch aerobus. it comes right to central area and you just ride it to the appropriate terminal

Far easier than that.... "at" Passeig de Gràcia you can catch both several metro lines as well as the train line. This train line serves also trains to the airport and there are no connections to be made, simply board an airport train in Passeig de Gràcia and voilà, you'll end up in Terminal 2 at the airport. Note though that if you need to get to Terminal 1 -most flights outside Europe depart from there- you'll then need to catch the free shuttle (green bus) that communicate both terminals every 5 minutes.

THank you all, I see clearly now how the connection works. I had read something that was misleading.

My wife and myself were there in September, very easy , a direct train ride into the Passeig de Gràcia stop . Walk up the stairs right into the street level .