To complete the upgrade:
Your current version of Windows 7 must be fully updated including all service packs.
(Control Panel -> Windows Update -> Install Updates, must be completed until all updates are installed.)
1. Click the Windows Start Button
In the search box, type Windows Anytime Upgrade
2. Click Windows Anytime Upgrade, then click Enter an Upgrade Key
3. Enter your purchased Upgrade Key. Click 'Next'.
4. Follow the instructions to complete the upgrade.
(Depending on your initial Win 7 installation, you may or may not have to 'Change product key' as well to the key purchased, on your System -> Properties screen in order to activate the new edition.)