Once you have completed your purchase of your AdSanity license you'll receive an email confirming your purchase with a link to your account where you'll be able to download the AdSanity plugin.
Should you misplace or delete that specific email you're always able to log back into the AdSanity plugin site and download the latest version of AdSanity. The login for your account is located on the main menu of the website. (fig. 1)
Once you're logged in you should be viewing your Purchase History (fig. 2) and you can click on "View Details and Downloads" to click through to your Purchase Confirmation. On the Purchase Confirmation page (fig. 3) you can click the "AdSanity" link to start your download. Note that the AdSanity link (and in fact all download links) will include the version number of the download. You can also access any Basic or Pro Add-Ons that are associated with your account from this same location.