For the audio track you want to use the mic with, you have to specify the input for the input port you plugged the mic into on your interface, and you also have to click on 'Input Echo On' for that audio track, to monitor the mic input.
This is also assuming you have the audio interface drivers specified in Preferences - if you do not then Sonar will have no idea that you have an audio interface.
Please post back with results as you try things - it is frustrating, but you are new to it, and there is unfortunately going to be a learning curve. FORTUNATELY, once you get things up and running, you will be very happy.
Bob Bone