RatePoint Support Center

First, go to "Emails," "My Campaigns" and click on the name of the campaign you want to re-send.  By default, it will take you to the "Reports" phase (the final phase of a campaign).  However, you can click on any phase you need to go back to by clicking the appropriate step on the Progress Bar (the green area that goes "Settings, Design, Content, Recipients, Send, Reports.")

So, click on "Recipients," and then add the new recipients you want to send to, click "Next" to go to the "Send" phase, and send the email just like you did the first time.  RatePoint will never send the same campaign to any recipient more than once, so even if you send the email to a group that received that email already, it will skip everybody except the new members of that group who haven't yet gotten it.

If you do intend to edit and send a campaign to contacts that have previously received it, you'll need to go to "Emails" and choose "Create."  Then, click "Copy an Existing RatePoint Campaign"
 and choose the email campaign you wish to work from.