OK need help with setting up FM transmitter.

So my 2005 325i doesn't have aux or Bluetooth installed..I went out and bought a Motorola roadster 2 which is a FM transmitter with Bluetooth capabilities. My issue is I am having a hard time finding a UNUSED station.my roadster is telling me to tune to 89.7 but every time I manually search for it it skips 89.7. I didn't know where to post this because I cannot find answer anywhere.. Thanks guys.