If you're accessing your email through "Google Chrome" ,
1. Open Google Chrome
2. Log into www.connect.xfinity.com
3. Stay signed in.
4. While you're in the inbox of your email, navigate through the settings of google chrome browser (It is located in the top-rightmost of the google chrome - below the "x" icon) go to "More tools" and select "Add to Desktop" there will be a pop-out somewhere in the middle of the screen and it will as you to add XConnect inbox(somewhat like this). It will let you add directly your email inbox in your Desktop using google chrome browser.
If you don't want to have that method above, you can actually use the windows live mail or Outlook 2016 (or any version i would prefer the updated one). Just add your comcast email in those Third-Party Email client, be sure to use the comcast username and password.