The home side took the lead in the 21st minute when Victor Wanyama sent a header past Barcelona goalkeeper Victor Valdes.
Tito Vilanova’s side came close to equalising before substitute Tony Watt came off the bench to double Celtic’s advantage, with Lionel Messi netting a late consolation for the Catalans.
“We thought we could affect them at corners, at the back post against Jordi Alba,” said Lennon.
“Charlie Mulgrew is one of best dead ball experts around, and Victor Wanyama gets better and better.
“We had to weather a storm, you know it’s coming and there’s not much you can do. Tony Watt gave us a new lease of life and scored a great goal. He’ll go down in the history books of the club.”
He added: “The club has been the in doldrums. This is not the pinnacle, there is more to come from this team, but the progression is great. It gives us a great chance [of qualifying].
“We go to Benfica next and will have to raise ourselves again, but we’ll cross that bridge when it comes to it.
“I want them to enjoy the moment and then get back to domestic action.
“When I came in I said I wanted to bring the thunder back and I’ve never heard anything like that.”
Meanwhile, Fraser Forster described Celtic’s victory as “tremendous” after the goalkeeper’s heroics at Camp Nou a fortnight ago were not enough to prevent a loss.
“Words can’t describe it,” said Forster.
“We put in so much effort away [at the Nou Camp] and couldn’t see it through, but today we have and we’re delighted. We have a fantastic squad; whoever comes in can do the job.”
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