To add or delete a page, you need to be on the Campaign Builder

If you're working from the Page Builder, click the [ < ] Back Button to go back to the Campaign Builder

If you're working from the Dashboard, simply click the campaign you want to work on to open the Campaign Builder

Add a Page

From the Campaign Builder, click the [+] button found on the bottom right of the screen to add a new page.

Delete a Page

From the Campaign Builder, click the "Page Actions" then choose "Delete" from the drop-down