During setup you can install SQL Server 2012 as Evaluation edition to test the product. What if you want to insert the license or upgrade edition? Few steps are required to complete the process.
Since Evaluation edition allows you to run the Enterprise edition for 180 days, you should check used features compatibility when changing edition from Enterprise to non-Enterprise to avoid issues.
Check running version
From SQL Server Studio Management right click the SQL instance and select Properties.
To check what edition is currently running, select the General page and look at the Product item. In this example the SQL Server Enterprise Evaluation version is currently installed in the system.
To install the SQL license or upgrade the current version, run Setup from SQL Server 2012 installation program.
Select Maintenance option and click Edition Upgrade.
On Setup Support Rules click OK.
If no errors, click Next to continue.
Enter the SQL license then click Next.
Check I accept the license terms item then click Next.
Select the SQL instance to upgrade edition. Click Next.
Setup validates the upgrade process. Click Next to continue.
Click Upgrade button to proceed with upgrade process.
When upgrade completes, click Close to exit the wizard.
From SQL Server Studio Management check again current running version. In the example, SQL Server 2012 has been upgraded to Enterprise edition.
The upgrade from Evaluation to a licensed edition of SQL Server 2012 is complete. You can use same procedure to change SQL Server edition as well but paying attention to used features.