How to delete an image from a gallery

First, hover over the image gallery section to reveal the toolbar, then click the Edit button.

Then, in the sidebar's Images tab, you can click the individual images you'd like to delete (holding down the Shift key to select more than one).

Next, click the Ellipsis button (...) in the bar above your images to reveal a menu.

In that menu, you'll see an option to delete the selected images.