If you have a favicon.ico file, you can now upload that file to your Apostrophe site, and it will appear next to your site's title in the address bar and in bookmarks (depending on your web browser you may see one or both of these benefits).
Next, click the left-hand menu on your website and pick "Customize Appearance."
Third, click the "Advanced Editor" heading. The advanced CSS editor will appear.
Now look over on the right for the "Upload Asset Images" button. Just click this button or drag your favicon.ico file to this area.
That's it! Close the editor and refresh the page and your icon will take effect. Again, some browsers show this in the address bar, others for bookmarks, others both. So don't be overly concerned if you see it in only one of these places.