On the site server, run .\BIN\X64\Setup.exe from the Configuration Manager installation folder. Use this copy of Setup because site maintenance options aren't available when you run Setup from source media.
On the Before You Begin page, select Next.
On the Getting Started page, select Perform site maintenance or reset the Site, and then select Next.
On the Site Maintenance page, select Upgrade the evaluation edition to a licensed edition. Then enter a valid product key, and select Next.