There are many ways you can tackle this. To get the right answer you need to be more specific.
What exactly are you hoping to achieve? Take/make handsfree telephone calls? Stream music from a device?
What stereo do you have at present? OEM? Aftermarket?
Also you appear to be confusing technologies. A USB port in the glovebox is a different solution to bluetooth. A USB port will enable you to connect a device using a wire. For example, in one of my cars I have a cable in the glovebox connected to the back of the stereo that enables me to connect an IPhone/IPad/IPod. Bluetooth, on the other hand, is a wireless technology. You could swap out your stereo for one with bluetooth built in or attach a bluetooth module to the existing stereo.
If you're looking to work with the OEM stereo then someone has already posted a guide for that:
Right heres my best attempt of a guide to fitting a bluetooth handsfree kit to a blaupunkt OEM head unit. The first thing to do is you have to wire the car kit up to the battery, pop the bonnet and locate the black plastic mesh in the top right...
www.fiatforum.com