I agree that PowerCMS is one of the easiest cms packages to set up.
When you bought it, and clicked download, there is a wealth of information on that page.
To get back to that page, log back in to your account in Webassist, Click on My Downloads. Choose PowerCMS from the list, then click on Support Resources on the left, then click on PowerCMS Help Resources.
Start with the getting Started Guide. In those pdfs on that page is all the information that you will need to set up PowerCMS.