You can add photos when you're creating the log. After entering the basic log information, you'll get to a Submit Hours button. Once you press that, you'll have the option to attach photos and/or share to your social networks.

You can also retrospectively add photos by going to your Activity Tab and editing a particular log. 

To add photos when creating a log:

Submit Hours --> Enter the Basic Log Information --> Click "Next" --> Use the Camera Icon to attach photos --> Click Submit Hours to Finalize.

To add photos to an existing log:

Activity --> Select the Log --> Click Edit (Pencil and Paper in top right) --> Click "Next" --> Click the Camera Icon to Add Photo