The Photo Capsule allows you to upload or import a picture or image into your Hub from your computer, from a URL (Web address) or Your Photos. Adding a relevant picture is the simplest way to liven up a Hub otherwise full of text.
You can toggle between the three inputting options (Upload, Import, and My Photos) to the left. Choose Upload if you're pulling in an image from your computer, Import if pulling in an image from a URL (Web address), and My Photos if pulling in an image from Your Photos on HubPages.
Only use images you have the legal right to use, and make sure you provide any necessary attribution for each image. For most Creative Commons-licensed images, you will have to name the source and provide a URL (link) to the source in order to fulfill the image owner's requirements, but every image owner's requirements are different for the usage of their pictures.
For more information on using images in your Hub, we recommend our two Learning Center entries: A Guide to Proper Image Use and How to Create Great Photos and Graphics: Tips, Tools, and Apps