On your booking site, some pictures of destinations will make your tour come nice and lively. When you add pictures on Gallery Manager page (by going to Tour and click on Manage button under Gallery column then click on New button), these pics will be available on your site as slideshow.
After clicking on New button, you can see a board with 3 fields: Title, Image and Description; Image field is required. You should pick "Select" button to upload new pictures from your computer and then click on "Save" or "Save and Close" button. You can upload many pictures but you have to do this many times (not once time). After that all of pictures you have uploaded will be available as a list on Gallery Manager page. From that page, you can publish/unpublish pictures, edit or delete pictures or choose any picture from gallery as featured (make any picture come bigger than other in the slideshow on your site)