[Sebastian]

As mcavour wrote, if you turn the ignition to the on position it releases the lifters. When the ignition is turned further, (like when the car is running), the lifters just go up and down. When you only turn the ignition to the first position they should retract into the body. Then you can slide the roof onto the deflector and drop it in place. If they don't move at all you are probably going to have to repair the sunroof drive.

There might be a way to retract them manually. Maybe someone else knows how.