Upload images in a gallery
In order to upload images in a gallery, click on PAGES (edit page) and select the gallery page in question. Click on EDIT CONTENT and then the button + UPLOAD IMAGES and select images. Select the images you wish to upload and click on Open. The images will be uploaded one by one in the order you selected them. When the images are uploaded you can reorder, delete and move images to a different gallery. You can also edit image title and description.
For videos, you can add videos to a gallery by clicking on + UPLOAD IMAGES and select ADD VIDEO. Enter the URL of the video in the field and click on ADD. The video must be uploaded on YouTube or Vimeo before you add it to your site. Also make sure that the sharing settings on YouTube or Vimeo are set to be public.