Using the Email Sign Up section

Your online store can benefit from adding a newsletter subscription form so that you can gather customer email addresses for email marketing campaigns.

Customize it in the theme editor to engage your customers by adding an image for better SEO, image shape, custom text, background, etc.

Note: When users sign up for a newsletter, they are added to your customer list in Shopify with the appropriate tags -"newsletter". From here, you would need to use some sort of app or newsletter provider and configure it to pick addresses with those tags from your Shopify admin and send out any emails.