By this stage you should have already chosen whether you will be including video with your recording or not, and will have a webcam available if you decided yes.
The window of the MDR will now be showing you the options for setting up the camera input, and the microphone input.
From the dropdown menus make sure to select the correct piece of hardware, as depending on your computer you may have more than one available. In the example screenshot, the MDR has detected that the computer has two microphones available, one in the webcam and one in the headset. As a headset will provide superior audio quality to the webcam in a video, make sure to select it.
Note in the screenshot above, I chose to record audio with slides, so a camera input will not be available. If I had it would appear like so: