How can I set up a footer with the text ‘keep me informed’?

You need to use MailChimp for this. If you are already using MailChimp, go to the settings module > social media. Enter the username and API key of your MailChimp account. Click on the option ‘Enable MailChimp’. Then tick this option: ‘Show registration form for newsletter at the bottom of the website’. Finally, set up a list with a name and selection for how all customers can see the form.