1. Click on the Media tab. Scroll through the list of media itmes on your page and check the "Address" for each item, making certain that the URL begins with "https://". Correct any unsecure image links.
2. If all of the images are called through the secure URL, click on the "Links" tab. Look through the list of "Addresses" for any items ending in a ".js" or ".css" file extension. Make sure that each is called through "https://".