Here are some resources to help you set this up. - Grow your Mailing List with Campaign Forms

Zoho Campaigns Course - Creating and Sending your First Campaign

This also has information on setting up contact lists and sign up forms: Campaign Help

Basically set up a mailing list, for example 'News and Updates' then create the sign up form. This will give you option to add a button or a form to any page of a website.

Happy learnings! :)