The 29-year-old Portuguese player was delighted with the move.
He said: "It's such a great club and there is the chance to fight for the championship and win cups here.
"When you join a club like Rangers, you can't expect anything but to win things."
He added: "Everyone here wants to be champions again and to bring happiness to the fans."
The former Porto player also feels his new club will benefit from his four-year experience of the British game.
"That will help," he said. "I know the game in England and the UK already so I'm already used to the British game."