Open Steam. Click "Games" > "Activate a Product on Steam."
Here is the trick: Enter the code exactly as it appears on the manual. Steam’s backend has a legacy translator. If the code has never been used in the old Relic Online system, it may convert automatically. Company Of Heroes Opposing Fronts Product Key Vs Retail Code
A Retail Code is the physical world’s lock. A Product Key is the digital world’s lock. They open the same game, but the keyhole is different depending on where you bought it. Open Steam