First, click on the photo in the timeline. Once the photo is displayed in an individual view, you can use the following approaches for sharing:

• In the app bar, you can trigger an upload to Twitter and Facebook. Please note that you will not be asked for any confirmation once you click the “1-click upload” button.
• In the app bar, you can also select “open with” and hand the item over to any desktop application that can handle the type.
• In Windows 8.1, you can also use the share charm to select any app that can handle photos appropriately, for example, the Mail application. Please note that the option does not exist in Windows 10.