If you are using the Image Manager, click the trash can icon under the image to delete it.
*Note. Any reference to this file on your website will display a broken image icon. If you are not unsure of the image use on other pages it is best to remove it from the page, but leave it in the Image Manager.

If you are using the File Manager, Click once on the file name in list view and then click the red X in File Manager toolbar. (below)

