Attachments are found where notes are on time records. You can get there from either the Time Clock screen or from the Time Sheet itself via the Time Details screen.
Click on the paper click icon to go to the attachments section. From there you can view the attachments in the list, or add a new one by clicking on the "+" icon in the upper right. This will bring up the Create Attachment view where you can elect to take a photo, pick a photo or attach a file.
You can see which time records have attachments from Time Sheets screen on the web dashboard. Any time records with a paperclip icon contain file attachments. You will also be able to see attachments as they are added in real-time from the Who's Working Now screen.
When viewing a time record, you can see the file attachments under the time punch it was attached too. Clicking on the attachment name will download that attachment to your computer. You also get a gallery view of any photo attachments on the time record under the map.
Attaching files can be done while editing time records.