Placing an image file

So I am new to creating an IOS app and have an issue when placing image files in the tabs section of a view. All of my images are just a Blue box when I run the app on the simulator. Can someone point me in the right direction?

What are the images you are using? Tabs for iOS are just outlines/masks, you cannot put an image in it.

Thank you Tim. This helps me a little further.