Hi,
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.
Theme Installation / Update
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.
Thank you.
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"Great looking feature rich and easy to use. For a beginner WordPress user, this theme has all the features and design needed to make a great looking website. " - 
"Fantastic. Easy. Modern. Love it. Easy to customize, great theme setting options. Much appreciated. " - 
"Love it. I've been using it for the last couple of months and I love it so far. There have been things I haven't like much, but with a couple of tweaks it is now the best theme I've ever used. " - 
"Slick, easy to use, looks great. Lots of great features but what I especially appreciate is the control panel is well laid out and easy to navigate. " -