After activating Redmix , 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 them and from the drop down select Activateand hit Apply
Required plugins: WPBakery Page Builder, Redmix Toolkit, and CMB2.
Recommended plugins: Contact Form 7, Newsletter and One Click Demo Import.