photo gallery

When I click movie maker button up comes

import from device and I the box of import photo and the video comes up blank where nothing shows in the box. Is there a web site that has easy directions for using photo gallery.When I select more and import my pictures ,then I save it and then go back the next day I can not edit the pictures.I seem to get mixed up .Also how many pictures will go on a DVD 4.7 gm.