The power cable of your system is also its FM antenna.
To optimise FM reception:
Make sure the power cable is not bundled up
Fully extend the power cable
Try moving the power cable 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.