Each template has default sets of pages and images which show what your website may look like when it’s built. You can easily remove this content and replace it with your own photos and texts. To delete the site page, in the admin area go to ‘Website” -> “Pages” -> drag and drop the page to “Trash” or simply click ‘Delete” button on the top grey panel.
To delete an image from the gallery, go to Media library -> click “All content” in the left column to see the all images in the library -> left-mouse click on the image you want to delete -> drag and drop it to “Trash” or click “Edit -> “Move to trash”. You can delete sets of the images the same way.