When you purchase MacWise from the Apple Mac Store, all downloads are done through the App Store app on your Mac.
Select App Store... from the Apple Menu on your Mac.
(Mac OS X 10.6.6 or later is required for the Mac App Store version of MacWise)

Purchase MacWise version 12 from the App Store

Purchase MacWise Version 15

10/1/15 Update...
The MacWise version 12 on the Apple App Store does not work with El Capitan.
You need version 15 for El Capitan and can purchase here

If you want to download the current version and try it out, the link is here...
MacWise Demo

When the demo expires, it will take you to an order form on the Carnation Software web site. If you would rather order from the Apple Mac Store, then order here.

NOTE:

Backup your existing MacWise application before installing the MacWise Demo.

The demo will overwrite your existing app.

(or you can always get the older app back from a Time Machine Backup)