“… I can’t enter a From Email Address on my Message ?…”
This sounds like you have not setup an Identity to send from, under the Tools Menu in GroupMail, Account Manager. Please enter your User Details [Name, From Email Address etc.. under the User Information Tab here then under the Delivery Options Tab enter your ISP’s SMTP Server details].
For steps on configuring your From Account in GroupMail, please go to http://group-mail.com/email-account-management/how-to-add-smtp-email-settings-in-groupmail/
If you have any questions or need some help along the way, don’t hesitate to contact our technical support team.