You can fork and issue a pull request to contribute data. Files are in the GeoJSON format. Shortly these will have the ability to be uploaded directly into the Atlastory database for rendering.
More info on the structure of the repository and contributing is in the Readme in the link above.
Brief tutorial on contributing to GitHub:
First: Although GitHub is currently the preferred method, if you want to contribute without it, upload your Shapefile or GeoJSON to a file-sharing service somewhere (Dropbox, etc.) and post the link to the forum. Someone here will be able to integrate it for you.
3/24/2014: Further changes to Github repo structure
- Step 1: Sign up for a GitHub account.
- Step 2: Download and install the GitHub desktop app for Mac or PC.
- Step 3: On the Base Map repo above, click "Fork", which creates a copy of that repo in your account. In your Github app, find the forked repo and click "Clone to Computer". This will download the folder to wherever you specified. There you can edit any file you need to contribute.
- Step 4: When finished, double-click the repo in the Github app. Go to "Changes" on the left, and write a quick summary of your changes in the input box, and hit "Commit". Clicking on "Sync" will upload your changes to Github.
- Step 5: In the main "Repositories" section of the app, right-click the base-map repo and click "View on GitHub".
- Step 6: On your base-map repo page, click "Compare and Review" (the green button), then "Create pull request" (another green button), then "Send" (the last green button). No we'll be able to look over and approve your contribution.
The folder structure was changed to sort maps under region > type > time period. This was changed to better match the structure of the future Atlastory database. So any GeoJSON added to the repo should be put into the structure of:
│ ├── admin-1
│ │ ├── 1871-1900.geojson
│ │ └── 1900-1910.geojson
│ └── admin-2
│ └── 1900-1920.geojson