If you come by plane to Barcelona El Prat airport, there's an Aerobús service that stops at terminals 1 and 2. The trip to Plaza Cataluña costs less than 7€ and takes 30 minutes. Your stop is Plaza Cataluña, and the hotel is just 10 minutes away.
The other option is to take the metro, green line (L3), and get off at Liceo Station.