I’ll update the instructions to be more precise, but you should “opt in” when activating the plugin, meaning you should click “Allow & Continue” on this: Screenshot
I missed the opt in on activation but I have now opted in via the plugins page. However I’m now following step 3 of your instructions for the free trail
Visit the Shared Files -> Settings -> Account -> Free Trial (tab) in your WordPress admin.
When I go to the settings I see the below tabs but no tab for “Account”
General settings – Layout – File type icons – Custom file types – Email Admin list & columns
Where can I find the “Account > free trial” tab?
You should find the Account-page (not a tab) under Shared Files on the menu: Screenshot