Connect a USB mic to the computer
Open System Preferences. Under Sound, set your Output to “headphones,” and set your Input to “USB”
Open Adobe Premiere Pro.
In the menu bar at the top of the screen, select Premiere Pro CC > Preferences > Audio Hardware, change the “Default Input” setting to “C-Media USB Headphone Set” and set “Default Output” to “Built-in Output”, then click OK.
In your timeline, right-click on the audio track header on the left, and select Add Tracks…
In the Add Tracks menu, set the placement of the track and change the track type to Mono. Click Ok.
When you are ready to record, click the voice-over record icon in your audio track header to begin and to stop recording.