1. Go to Funnels and select a funnel that you've already created to start editing it.

You can also click on "Edit" in the dropdown menu to do this.

2. Under the landing page step of your funnel, you have the option to add an internal step.

Click on "Add internal Step" to do so.

3. You have the option to add a popup as an internal funnel step.

So, select one of your ready popups or use a template.

Tip: You can add more than one internal step to a landing page.

4. Once you add an internal step, an arrow icon will appear to the left of the landing page thumbnail.

Click it to expand the list of this landing page's internal steps. 

5.  When you're done adding the internal steps, you can either click "Launch the funnel" or go back to your list of existing funnels.