Instructions: 1. Once you purchase an MSFS product on Simmarket, you will be prompted to download the Contrail app. 2. Download and install the Contrail app. 3. Open Contrail and select the developer, then the product you'd like to install/activate. On the product page, click "activate"4. You will be prompted to select where you purchased, click "Other Shop"5. Enter the serial number you received from Simmarket6. Install and fly!