You can find and sign up for Cooki at cookihq.com.
Installing on Shopify
Once you register for a Cooki account at cookihq.com, click "Account" and add your myshopify domain to the Store URL field. Click Authorize with Shopify and follow through to your Shopify account. Voila! You're installed.
Creating your notification banner
Once you have authorized with Shopify, click Notifications and then "Add A Notification". You'll see a standard banner appear that looks like this:
From here, you can click "Edit" to update your settings.
In "General Settings" you can select the option to only show for European customers, update the background colour, and select the banner's orientation (top or bottom of page) and padding.
Clicking "Description Options" will allow you to update the description text.
Finally, clicking "Accept Button Options", "Decline Button Options", and "Info Button Options" will allow you to change each button as well as allowing you to hide the More Info button from the banner.
Adding the banner to Shopify
All you need to do now is click "Activate on Shopify" and Cooki will appear on your store. You can click to activate on the notifications main page or from the editing page.
If you wish to add this banner to a theme that doesn't support script tags, you can copy the text in the box at the bottom of the edit page and paste it at the foot of the liquid file you wish to show the banner on (before the closing body tag). See here for more information on how to edit your theme.
Adding the banner outside of Shopify
This banner can be used outside of Shopify, to use it on another site like a blog, marketing site etc, just copy the text in the box at the bottom of the edit page and paste it into your website's HTML. Any page that contains the pasted script tag will display the banner.
To uninstall a manually added script from your store, simply remove the pasted script tag from the liquid files you added it to. The script tag can mostly commonly be found in the head or just before the closing body tag.