Lennon's side eased to a 3-0 victory in the first leg of the tie in Belfast, thanks to goals from Mikael Lustig, Georgios Samaras and James Forrest, six days before the return game at Celtic Park.
The sale of Victor Wanyama to Southampton for £12million means that the SPL Champions have significant transfer funds available, and Lennon says he wants to utilise them as soon as possible.
"Hopefully we've negotiated the tie but we need new bodies in for the next round and we're going to do that," he said after the win.
"We're actively looking at strengthening the squad as there's money available from the Wanyama transfer.
"I'd like someone in before the second leg next week if I can so we can bed them in as quickly as possible. If we could get one in early next week, I'd be delighted but at the moment we aren't close to anything."
Meanwhile, the future of highly-sought-after striker Gary Hooper has been the subject to further speculation with QPR reported to have joined the chase for his services, but Lennon says there has been no progressions.
"Talks are still on-going between Gary and his representatives but no bid has been accepted by us yet," he added.