You can create an opt-in form in 2 easy steps: 

1. Create Free Product
2. Add a free product payment button to your page

1. Go to the website you want to add products for sale.

2. From the left sidebar, click on the Products.

3. On the products page, click on the Add Product button.

5. Select the Free product type from the options.

6. Input the free product details: Name (e.g. Newsletter), Description and more.

8. Click on the Add Product button.

1. From the left sidebar, click on the Pages.

2. Click on the page you want to add the product.

3. Select a button or link to turn into an opt-in form trigger.

4. In button action, select Products.

5. Select the free product you've created from the Select a product dropdown.