After activating Polygon, you will see this notice:
Click Begin installing plugins. You will be navigated to Install Required Plugins page.
Simply check all of them (or all of required plugins and some recommended plugins you like) and from the drop down select Install, then hit Apply.
When finishing, it should look like this:
Next, go to Plugins >> Installed Plugins check all of theme and from the drop down select Activate and hit Apply
Required plugins: ThemeMove Core, WPBakery Visual Composer, ThemePunch Essential Grid, ThemePunch Slider Revolution, WPBakery Templatera.
Recommended plugins: Contact Form 7, Testimonials by WooTheme, WooCommerce, Widget Logic, Loco Translate.