If you’re using a site with a CMS, you probably already have a default favicon that you’ll want to change.
To do this, you need to search for the favicon.ico line in the source code, and you will see in which folder the current favicon is loaded.
The easiest method is to upload your favicon.ico via FTP to this folder (which you found by searching in the source code of your website). An important point: in the browser, you most likely will not see changes due to browser’s cache. You can check whether the image was loaded normally or not by clicking on the particular link to this icon (as you remember, you already found the link in the source code). If you press Ctrl F5 several times, the browser cache will be cleared and the new favicon will be shown in the website tab.
If your website does not have a favicon at all, you need to upload it via ftp, or through the File Manager, and then add the code in the site template in the head section:
<link rel="icon" href="favicon.ico" type="image/x-icon" />
In the href value, specify the path where you uploaded the icon. If you uploaded your icon to the root of your site, then changes in the example above are not needed.