To embed a signup form for your Substack publication head to your Settings page and click on Import your email list in the left navigation bar. In this section, you'll see a unique code for your publication (see below for an example).
Insert the HTML code onto any website to embed a signup form for your Substack publication.
Note: Our embedded signup forms work on any platform that support HTML IFrames (Wordpress, SquareSpace, custom websites, etc.) but this excludes Medium.
Currently, the embedded signup form is not customizable at this time.