Your Site Icon, or Favicon, is the small version of your logo that appears in the tab of your web browsers. This adds a nice finishing touch to your website and makes it easily recognizable when someone has multiple browser tabs open.
In your Design & Themes Customizer, select Add Your Logo
Remove the default icon
Click Select Image and drag and drop your Icon to upload
Click Select and and Crop Image or Skip Cropping
Publish to save your changes
Screenshots of how to change your site icon (favicon)
You can do this by going to your dashboard, selecting "Design & Themes"
Click "Add Your Logo" on the left.
Click the "Change Image" button and upload your site icon (it should be at least 512x512 pixels).
After you upload your new site icon, click Save at the top left of the editor.
Here's a view of your site icon (favicon) in your browser tab.