Put your Hub in edit mode by clicking "Edit" at the top of your Hub or start by making a new Hub.
If your Hub doesn't have a photo capsule, you can add it to your Hub by clicking the Photo Capsule on the right hand side of the page.
Once the capsule is added, click "Edit" on the capsule. This will bring up a selection box to add a photo from your computer or from the web. If you want to add a photo from the web, you'll need to know the URL to the photo. Then click the load images button.