The 31-year-old Ghanaian forward sealed a sudden loan move from Serie A side Sassuolo on Monday for 1 million euros with the option to move permanently for 8 million in the summer.
Boateng, the former Tottenham, Portsmouth and AC Milan midfielder, says he can add know-how as Barcelona set their sights on another treble.
"I haven't spoken to the coach (Ernesto Valverde) but I know I have not come here to be a starter because there are incredible players in this team," Boateng told reporters at his presentation.
"I am here because of my experience and to help out. When I heard the news I called my agent and thought it was a dream.
"It's an incredible sensation. Yesterday morning I was sad because we had a good group (at Sassuolo) but I explained to them that coming here was an opportunity I couldn't refuse."
After selling Munir El Haddadi to Sevilla, Barcelona needed to sign back-up for Luis Suarez and they settled on Boateng after being linked to Carlos Vela, Alvaro Morata, Cristhian Stuani and Cedric Bakambu.
The Spanish champions wanted to sign a player who has experience in the top flight, and Boateng impressed with Las Palmas in 2016-17 before moving to Eintracht Frankfurt for personal reasons.
Boateng, who operated in attacking midfield before converting to a false nine role, has also played in England, Italy and Germany.
"At my age the false nine position is perfect for me," added Boateng. "The coach might think having a player like me is a positive because I can play in different roles, but I feel very good as a forward."
After breaking through at Hertha Berlin he moved to Premier League side Tottenham, later featuring for Borussia Dortmund and Schalke 04 among other sides.
Asked about his previous praise of Juventus and ex-Real Madrid striker Cristiano Ronaldo, Boateng joked that new team-mate Lionel Messi is the best player ever.
"I'm a Barcelona player and the best player in the world is Messi, in every world," said Boateng.
"He's shown it with all he's won over the years."
(Reporting by Rik Sharma; Editing by Hugh Lawson)
