Hi Rosalind,
To be sure you know what you're getting into:
ListMail is a 'script' (a bunch of files to be uploaded to your site) not a 'program' for your Windows or Mac computer. It's installed on your web host(~$10/mo)/domain(~$8/yr) and sends email through your host. You can access ListMail from anywhere you can reach your web site.
Do you currently have a web site? If not, do you have interest in setting one up for ListMail?
To download ListMail look for the "Download" section in
the member area. Installation documentation can be found at
http://listmailpro.com/help or web hosting + installation assistance can be purchased for $50 from
http://listmailpro.com/supportRegards