It's still not entirely clear to me what you're asking, but it seems like you want to add a favicon to your website. If that is the case, there are basically two approaches you could take:
- The simple, but deprecated method is to put a file with the basename "favicon" (e.g. favicon.ico) into the document root of your website.
- The preferred method (according to the W3C) is to reference the icon file with a <link> tag. In Q2A you'd add something like the following via Administration center → Layout under "Custom HTML in <head> section of every page":
<link rel="icon" type="image/png" href="/path/to/icon.png">
The format of the file should be either PNG, ICO or (static) GIF. Some browsers also support other formats like JPEG or SVG, but that is not standard so you should refrain from using those.
The size of the icon must be either 16x16 px or 32x32 px with either 256 or 16M colors (8 bit or 24 bit respectively).
For further information see the W3C Howto.