Getting CKEditor to work in MAILpress plugin

I have a plugin called MAILpress installed on my WordPress site. The CKEditor works for the Wordpress posts but not when I add a mail message with MAILpress. I get the default TinyMCE enditor instead.

The developer of that plugin said: "adding the MailPress admin page (in CKEditor plugin php code) would help to get CKEditor available."

Do you know how I would get the CKEditor to show up in this plugin?

Thank you very much!

-Martin