To add content to the gallery, select the Gallery tab on the left.
Then select Upload to choose media to add to the gallery. Browse to the media you intend to add (video or images) and click upload. Wait for all files to finish uploading, then click close.
Files can be deleted or replaced within the gallery at any time.
Replacing a file will also replace any instances of that file within all playlists with the new replacement.
You can edit the properties of any number of these files at once by selecting their tick-box and clicking edit.