You can submit data to be included in the data repository going to File > New > Data Resource.
Alternatively you can see this Stack Exchange article which covers how to do this: https://mathematica.stackexchange.com/questions/143618/adding-computer-vision-datasets/144126#144126
Hi Sean, is there any difference between method suggested by MSE and by Stephen Wolfram in his blog:
http://blog.wolfram.com/2017/04/20/launching-the-wolfram-data-repository-data-publishing-that-really-works
I wouldn't worry about it. They don't really differ that much except in how to bring up the notebook that you fill-out and submit.
If you have any questions about any of the fields, please let us know.