Login with your main account's username and password at the Customer Control Panel
Click on the "Websites" tab.
Click on your domain name.
Click on "Web Hosting Settings".
You'll see all the different types of coding that is enabled on your site under Basic Settings.
At bottom of page you'll see the "Edit" button, click on that button.
From the ASP.NET Support section, you'll see a drop down box, select ASP.NET 4.0, then click the submit button.
You've successfully enabled ASP.NET 4.0 for your site.
Any account before February 9th, 2015, if you don't see this option under these settings, you'll need to send an email to email@example.com to request ASP.NET 4.0 to be enabled for your POA account.