Hi Marjorie,
I don't think there's a way to actually *change* your Yahoo ID, but what you might want to do is set up a new one if you don't want to keep using the one you're using.

If you go to http://groups.yahoo.com if you are logged in it will have your Yahoo ID displayed somewhere near the top of the page. Click the link that says "Sign Out".

Then click the link that says "Return to Yahoo! Groups"

You will see the sign in page - underneath where you sign in, there's a link that says "Sign Up". That will let you set up a new Yahoo ID.

Or if you are not logged in, just go to http://groups.yahoo.com - it will take you to the sign in page and you can click the "Sign Up" link.

When you click the "Sign Up" link it will step you through the process to set up a new Yahoo ID.

After you do that, you will want to sign up for whatever lists you have using the new Yahoo ID you set up. Even if you are a member under the old Yahoo ID, you will need to use the new one to sign up.

If you are trying to change your Yahoo email address, I can't really help you with that, though I imagine it would be similar.

Hope that helps,
Kitty