1/ Turn the phone on and activate bluetooth
2/ Turn ignition in vehicle to accessory
3/ On your phone, select 'Search devices' or whatever you select to look for other bluetooth devices
4/ Your phone should see 'Vehicle BT'. This is your car's bluetooth signal.
5/ Select it and pair with Vehicle BT. The owner manual states to use the password '1234' which is just something generic to pair with the devices.
6/ Once the connection is made the car's bluetooth will turn the CD/Radio music off and switch to Voice. You'll notice it when your speakers make a slight whine that sharply increases and then dissappears quickly. That's just the head unit adjusting the gain from the signal it receives from your phone when someone talks to you. For the SSV model, you should see Voice In displayed on the screen when this happens.
7/ Now that the phone is paired with the car (You can pair more phones if you like at the same time) the car's bluetooth takes care of the rest. You'll hear the receiver in your car's speakers and the microphones are located near the overhead interior light. So you just need to go on your phone to activate a call and that's it.
8/ As for the call button on the steering wheel - If you are receiving a call, you'll see a phone symbol on the instrument cluster dot matrix. Push the steering wheel button once to pickup or hold it to hang up on the caller during ringing (teeheehee). If you made a call before on your phone, press the button twice to redial that number and the phone symbol on the instrument cluster dot matrix will appear.
I'm just going off for memory with the bluetooth in my SSV. Please correct me if I'm wrong as this info might slightly differ for the Omega but I believe that the system is the same throughout the model range. It also helps to consult your vehicle's manual if something doesn't make sense.
Hope this helps.