How do I take proper measurements to make sure they fit? Do I measure inside the frame.

Thank you for your question. The recommended window depth for this item is 1 inch. For an outside mount, measure the width and height of the area you want to cover. This is your ordering width and height. For an inside mount, we recommend that you measure in 3 locations: top, middle and bottom of your window and use the smallest of the 3 for your common width measurement.