To upload photos and videos from your devices Camera Roll tap the Action Menu and the ‘ ADD FILES’.
Note that the Action Menu chevron has now been replaced (as of iOS app v4.3.1) by the ellipses button
Then tap ‘ UPLOAD FROM CAMERA ROLL’
You will then be presented with a view of the photos and videos in your device’s Camera Roll. Select the photos and videos to upload and then tap ‘DONE’. These will then be copied to the destination from which you instigated the ‘ADD FILE’.
By long pressing on an item and dragging around the image picker above, you can select multiple items without having to tap each individually.
It is possible to select all items in the Camera Roll by tapping the chevron / ellipses button top right in the image picker window >> SELECT ALL. From the pop-up menu you can also deselect all.