Once you've created a patch the best way to submit it is to raise a new issue in the issue tracker (see below) and maybe send us a mail on the developer list letting us know about the patch.
Submitting Github Pull Requests
Another way of contributing code to the project is by submitting a Pull Request to the project on Github.
The best workflow for this is to raise a new issue in the tracker (see below), fix the code in a branch on your forked project, and submit a pull request via the Github UI (mentioning the Jira Issue ID in th pull request, and then commenting the Jira ticket with the ID of the pull request so that both can be tied together).
One workflow you could use is described in a blog post here.
Using the issue tracker
Before you can raise an issue in the issue tracker you need to register with it. This is quick & painless.