And the Celtic boss wants to use the cash to bring in at least two more players in this window.
Johansen and Holmbert Fridjonsson - the Icelandic striker acquired from Fram Reykjavik for £100,000 - are the first names to be added to the squad this month.
But Lennon - who was at the Fulham v Norwich cup tie in midweek - is far from ready to put away the cheque book.
"We will try to bring in a striker and another forward, an attacking midfielder type," said the manager.
Lennon insists he doesn't need to move anyone out before he can continue buying, and that the arrival of left-sided midfielder Johansen does not mean Joe Ledley is heading for the exit.
The Welshman is edging closer to agreeing a new contract to replace the one set to run out at the end of the season.
But Lennon - who was named Manager of the Month for December while Kris Commons lifted the Player award - reports there is no progress in getting Georgios Samaras to commit to a new deal.
Lennon is aware contact has been made with the Greek striker's representatives - Atletico Madrid still lead the chase - though none have got in touch with the Parkhead club.
If he is not going to re-sign, Celtic would prefer to sell now rather than allow him to wind down his contract and leave for free in the summer.
Lennon said: "We don't know where we are with Georgios at the minute.
"The signs from Joe are more positive, but, again we don't have any confirmation of that.
"There are no deadlines, but the longer it drags on, the more speculation there will be, and we could do without that."
Asked if there has been interest in Samaras or Ledley, Lennon replied: "Not to us directly.
"Certainly, there has been contact through Georgios's agent, but we haven't had any confirmed bids for him."
If Ledley and Samaras reach the end of this month still refusing to sign new deals, Lennon admits he will have to decide if they remain in his side, or if he goes with players he knows will be here for the Champions League qualifiers in July.
The Hoops boss said: "They are good professionals and I wouldn't imagine they'd hold anything back.
"But, if they are going to run down their contracts, then, obviously, they will not be here next year."
Meanwhile, overtures from Wolves to take Callum McGregor on loan are being rebuffed. Lennon wants the attacking midfielder to remain at Notts County, where he has been delighted with the progress he has made in the last six months.