Once you've created your Signup Form you can add it to your Email Marketing campaign using a subscribe link. There are two main ways to add the subscribe link to your Email Marketing campaign.
Anywhere you add [[subscribe]] or [[subscribe_link]], Email Marketing will replace it with a link to your current Default Signup Form. This works for both custom HTML campaigns and the regular composer.
Each signup form has a unique share URL. You can add this URL to any text module in your campaign. The share URL always links directly to the online version of your form.
Go to your Signup Forms area, and click on the Share button underneath any of your forms, to grab the share URL for that form.