The Belgian winger, who arrives from Club Brugge in a deal worth around €8.5m plus add-ons and has signed a contract until 30 June 2031, posed for photos alongside club president Joan Laporta and the club's sporting leadership before speaking to Barcelona's own media.
Flick made the call to fold Bisiwu into first-team training after watching him in action during his opening sessions with the squad, though the 18-year-old could still be registered with Barca Atletic depending on how the season develops.
"When I was young, I always dreamed of playing for a big club like Barca, so being here is a dream for me," Bisiwu said, reflecting on a move he has been working towards for some time.
On his early impressions of working under Flick, Bisiwu added: "Flick has welcomed me really well. We've already had a few chats these days. It's easy to understand what I have to do this year: work very hard and learn as much as possible."
He also spoke warmly of his reception from team-mates and staff since arriving at the club.
"Everyone has welcomed me really well and been very attentive. I feel like I'm part of a big family and I'm very grateful," he said, before setting out his ambitions for the campaign ahead. "This season I'll work hard and want to give my best. We'll see how the season develops. My idea is to give everything for this badge."
Bisiwu becomes the latest product of Club Brugge's academy to make the move to a major European club, having impressed in the UEFA Youth League and drawn interest from elsewhere on the continent before Barcelona moved to secure his signature. His versatility across the front line and turn of pace were cited as key factors behind Deco's push to get the deal done quickly, with the sporting director keen to give Flick another attacking option to call upon as pre-season progresses.
Whether Bisiwu features regularly for the first team or spends the bulk of the campaign with the reserves will ultimately be Flick's call, but Tuesday's presentation confirms he will, for now, train and travel as part of the senior group.
The move continues Barcelona's recent pattern of moving early and decisively for teenage prospects from around Europe, with the club's recruitment department having identified Bisiwu as a priority target some months before the deal was finalised. Reports in the build-up to the transfer suggested Barcelona had been tracking his progress since as early as December, holding regular dialogue with his representatives before agreeing terms with Club Brugge over the summer.
His arrival adds further depth and competition to a Barcelona front line already stocked with young attacking talent, continuing a trend under Deco's sporting direction of blending experienced first-team players with academy graduates and low-cost teenage signings from across the continent.