The Usergrid project has adopted a policy for how code is to be contributed by external contributors, and by those who are committers on the project. You can read this policy here Usergrid Contribution Workflow.
Basically, we use GitHub as our code review system. So you should fork the apache/incubator-usergrid repo and submit PRs back to the project. Here are are step-by-step guide for both both external contributors and committers:
If you want to contribute to the documentation you‘ll find that we use a different system. Our website and documentation is managed in Subversion. Here’s a README file that explains how to get the website and documentation source code and make changes: