First click on the "Edit Page" button across the top and make sure you are on the right page.
Then you can add a new frame by clicking "Add Frame." This will generate a frame in the middle of your spread. You can change the size of that frame by clicking on the circles and dragging and dropping.
You can also create frames by holding and dragging your mouse anywhere on the spread that's not occupied by an existing frame or text.
If you have any additional questions, please email firstname.lastname@example.org