Administrators can manage the icon used as their campaign site's favicon via Site Builder.
To add or edit your site's favicon, click the image icon in the Site Builder bar, then click the "Favicon" tab. You can select an image from your computer or drag and drop an image onto the uploader. It is recommended to upload a transparent PNG file that is 256x256 pixels. To remove an existing favicon, simply click "Remove" to the right of the listed favicon.
Please keep in mind that your changes are not saved on the site until you click "Publish" in the Site Builder bar.