mysiteurl.com/url.html– URL which will load when someone clicks on the image.
You may look for a plugin that provides the same functionality. Such plugin is the Image Widget. After you install and activate this plugin, the Image Widget will be available under Appearance -> Widgets menu.
Place the widget in the website section where you want the image to be displayed (e.g. sidebar area). You can select an image from the Media Library or upload a new one.
The image settings enable you not only to link the image to a specific URL address that will be loaded when it’s clicked, but also to specify whether the URL will be opened in a new or the same window and to add image size, alignment and title.