The task was done over several hours in the middle of the night as astronauts used robotic arms from both the shuttle and the space station to lift the AMS out of the shuttle’s cargo bay then maneuver it into place and install it on the station. They were finished by 5:46 a.m. Eastern time.
The report also stated that it has already been "turned on", whatever that means. I'm sure there's a lot of diagnostic checks and calibration being done before actual data-taking.
Check out the AMS on-orbit images at the AMS homepage.