Add a media
To add a media (image, video, sound, etc), click on the button on top of the media panel (left panel).
Click on one line of the open dialog to choose the type of media you want to add (stereo in a single file, stereo in two files, 2D image, etc):
Choose a file on your disk:
Click on the "Open" button.
If two files need to be opened, do this twice.
The media should appear in the open dialog box and in the media panel (left panel):