Please read this Reddit post for instructions.
You can suggest new entries to the Atlas for art that isn't mapped yet, or update entries by editing it.
Click anywhere on the image to start drawing a shape. Switch between periods by adding a period, and/or seek through the timeline.
When you're happy with the result, click the "Finish" button above. You can then add more information about your object.
You can ask for help on our Discord server!