Your existing theme is too old, and it does not contain the automatic update code and settings.
You need to do a manual update to current version 2.6.8 in order to see the Appearance -> Theme Updates settings.
Manual theme update information is found at the end of the following article.
Please use FTP to backup your existing Evolve plus 2.0.1 onto your desktop before you do a manual theme update. In case you do not like the current version, you still have your old version to fallback.