In the power mailer admin section, there is a Mailings -> Groups menu item where you can define the groups.
once a group is defined, there is a button next to the group for "Get Signup Form HTML"
place this sign up form on the pages of your site to allow users to signup for the mailing group.
The licensing for power Messenger is for a single domain, we offer a volume licensing program where you purchase additional licenses at a discount:
what browser are you using to view the WebAssist.com site?
i just did a quick test in the major browsers, Safari, Chrome, Fire Fox and IE, and do not have a problem viewing the Power Messenger page.