I've read other posts on the topic.
I did that way
# Make sure it is named favicon.ico
# Upload it to the home directory of your site. E.g.: http://op111.net/favicon.ico
# Install and activate Extended Options
# Go to Dashboard, Settings, Extended, Favicon Meta Links
# Select “Favicon in root directory”
# Scroll down and click Save Changes
The favicon is dispalyed in the preview, but doesn't show on browser (Safari and Firefox).
Theme used is Technical speech