The power cord of your system is also its FM antenna.
To optimize FM reception:
Make sure the power cord is not bundled up
Fully extend the power cord
Try moving the power cord around
If FM signals are particularly weak in your area, you can also enhance reception by purchasing an external FM dipole antenna (click on the Parts/accessories tab above). Plug the external antenna into the 75Ω FM ANTENNA jack on the rear panel of your system, and extend it as far as possible from the unit and other electronic devices. Attach it to a wall, behind a table or under a cabinet.