I cannot log into comcast email.

To migrate to Yahoo, assuming your email account has received the invitation already you will need to login to https://www.xfinity.com/email and then follow the steps using the banner on the homepage.

More information on transitioning the email to Yahoo can be found here: https://www.xfinity.com/support/articles/yahoo-email-migration-overview

You mentioned having issues trying to log in to the email. Did you forget the password? How do you normally access the Xfinity Email?

Concern moved here to the E-mail help section.

@user_2be172 

I cannot log into my comcast email. I can receive Xfinity mail. 

Do  I need to sign up for Yahoo to get my email? If so, how do I do that?

FWIW Comcast = Xfinity

Your email address is xxxxx@comcast.net not xxxxx@xfinity.com.  If you haven't migrated to Yahoo! Mail yet [no, you do not need to sign up for Yahoo!] you will find your @comcast.net email here:  https://connect.xfinity.com/appsuite  

Are you using a third party email app like Outlook, Thunderbird, Apple/Mac mail?