The first leg of the encounter takes place in Naples on Tuesday and Muniain has insisted that the Basque outfit are "prepared" for the clash.
"We're really looking forward to the game. We've waited so long for this and we've prepared very well for the tie," Inside Spanish Football quotes the Spaniard as saying.
"We've played a lot of games in pre-season and we're really enthusiastic about getting into the game against Napoli and into the stadium there."
Bilbao finished fourth in La Liga last season.