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If your PC has 2018 or 2018b installed
Run the setup file for Origin 2019 to start installation. You will not be asked to enter a Serial Number. The Serial Number and license will be obtained from the 2018/2018b installation automatically.
You can work with Origin 2019 right away after installation.
If your PC does not have a previous version, or the version is older than 2018
Run the setup file for Origin 2019 to start installation. You will need to provide a Serial Number that is valid for Origin 2019.
After installation, run Origin, and you will see a License Activation dialog. Enter a Product Key to activate Origin. You can find a Product Key in your license management page: https://www.originlab.com/reginfo