The dongle is compatible with the OBD II protocol. It is plugged into the OBD port of your car. The OBD port looks like this:
http://www.wikiobd.co.uk/ is a very reliable and extensive source of OBD locations in different makes and model.
The OBD II port can be found within 90cm (3 feet) of your steering wheel. Check in the following locations:
If you are still struggling to find it, then google it as follows: "obd port location <make> <model> <year>", so if you had a 2015 Ford Mustang, you would google "obd port location Ford Mustang 2015".
If you still can't find the OBD port location, please contact us at firstname.lastname@example.org and we'll help you out.