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Run Origin after installation, and enter a Product Key in the License Activation dialog that opens to activate Origin. You can find a Product Key in your license management page: https://www.originlab.com/reginfo
NOTE about User Files Folder (UFF)
This beta version uses a new, hard coded UFF location (.....\documents\Originlab\2019 Beta UFF\)
We did this to avoid any issues with sharing UFF with older versions.
If you need to use your custom files such as themes, fitting functions etc, you can use the "Tools→Transfer User Files" menu item in Origin to copy your user files from older version to 2019.