You can add a notification about cookies usage of your website, you should place a text widget with such warning on a separate page. Once the new page is created, you should make it your site homepage (you can do this by choosing the page you recently created from a dropdown list in Preferences -> Website Preferences -> Website homepage). When a visitor opens your website, he'll see this page with cookie notification (mean the warning description you created) first of all, and then it's possible to move to the other pages of your site.
As an alternative, you can use some custom plugin with warning - please use HTML widget in order to add custom HTML/JS code. HTML widget lets you to run any HTML5 compatible code or JS script.
Please note! MotoCMS uses moto_cms cookies that are required to run MotoCMS admin panel only (website backend). We don't collect, save or store any personal information (such as cookies) in our templates. However, client can add some custom code or scripts to the website by himself (such as social media plugins) - in such cases you should contact the developers of this code or script to obtained information about cookie usage and cookie law compliance.