Step One:
First look to the icons in the bottom right hand of your screen. You should see a blue circle with a lightning bolt. Single click on the lightning bolt icon.Step Two:
Click on the "Device O:" option. This should open a new window where you can navigate to the location of the .iso, .mds, .cue, or .nrg file. For example, if the image file is in your Downloads folder, you will need to navigate to the Downloads folder and select the image you are trying to mount.Step Three: