The Senegal international told the Daily Record: "When my manager at Charlton told me Rangers were interested in me I immediately telephoned my friend Jean-Alain.
"He told me great things about the club, the stadium and the fans. He said everything about the club was good. I got on to my agent and said, 'I must go to Rangers'. I wanted to run to Rangers there and then.
"I feel I can do a great deal for Rangers. The fans must know I'm the type of player who gives everything on the pitch to help my team.
"That's my style and I hope to show the supporters that."