TechNet has an article for this that start with point 1 and ends on point 2. http://social.technet.microsoft.com/wiki/contents/articles/16033.sharepoint-2013-migrate-from-sharepoint-foundation-2013-to-sharepoint-server-2013.aspx
This is not very explanatory. There are other articles too that talk about only for upgrading from SharePoint Foundation 2010 to SharePoint 2013 but none of them talk about SharePoint Foundation 2013 to SharePoint Server 2013 Enterprise.
We have currently Foundation 2013 installed on our server.
Also I can see in Central Administration there is 'Convert Farm license type option' under Upgrade and Migration.
So just by providing the license key is it possible to upgrade from Foundation 2013? or we need to follow the steps from TechNet article?
Which one if true and How we can achieve the same?