Hi Kathy,
Just go to the page for the group. If you haven't been there before, an easy way to find it is go to http://groups.yahoo.com (you will have to log in using your Yahoo ID and the password you set up for your Yahoo ID).

It will give you a list of your groups.

Go to the one you want, and near the top of the screen there will be a link called Edit Membership.

When you click on that it will give you the choices how to get mail. Sounds like you want the Daily Digest.

Kitty