Many of us used to Google groups can actually use our Google account ID to log in here. Others may discover other options they understand in the drop-down menu asking for your "profile" before you post a comment.
Currently, you won't find "Yahoo" as an option on this page, but in fact you Yahoo users may already have a profile you can use here. [I just reviewed the login options today. As of 12/1/15 — and probably long before then — you can also log in with Yahoo directly without Open ID!] In your Yahoo settings, just sign up for "OpenID®." In fact, several different services now support "Open ID®."
You can check more intelligent and informed details at this web page about OpenID® .
Let us know how it works or what other hints you have for us blogger newbies!