Assuming you have all the BT(bluetooth) module installed...
Below has worked for me after searching for awhile...

Below is from memory...

1) press and HOLD the R/T button on the steering wheel, then insert key and turn to the ON position and you're still holding the R/T button!

2) start the BT scanning from your cellphone(assumed you already have turn on your BT on your cellphone.

3) you should get a device called "BMWxxxxx" that xxxxx is your last 5 digit of your VIN #. Keep holding the R/T button!

4) then your cellphone will prompt for the PK#, enter that in then wait for it to complete the PAIRING, still holding the R/T button down!

5) Now you should NOT see the red light on top right of the headunit, it should go away

6) release the R/T button, and wait for a few minutes(+/-) as it copies all your contacts to the head unit/storage.

From what I read you can pair up to five(5) cellphones.
For me I've successfully pair my Galaxy Note 2.
Will pair my wife's iPhone5 later on.

Please correct me if i missed anything on the instructions.
Good Luck!!!!

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2005 X5 E53 4.4i(Prod date: 12/20/2004),
Fully optioned w/o heated steering /
Navtool + backup camera coming soon /