If you want to contribute code then the best place to start is by looking at the project's issue tracking system. Here you can find issues that are unassigned or need completing. You should then post a message in the project's development forum with a reference to the issue asking if it can be assigned to you.
If you want to make a contribution but there are no relevant issues then post a message to the project's development forum asking if one can be created.
Using the development forum in this way helps to keep the issue tracking system tidy and accurate as issues are only assigned or created after discussions have taken place.
Note: Before you start contributing code it helps to have an idea of how the current codebase is written, together with an idea of how the community works together to get things done. The best way to do this is by spending a few days to read the project documentation, study the existing code, and watch the activity on the wiki and forums.
Before we can accept any code contributions you need to have signed a Contributor Agreement. This sets out the terms and conditions under which your contributions will be used within a project. If you wish to make contributions outside of working hours then an Individual Agreement should be signed. Alternatively if you wish to make contributions during working hours then a Corporate Agreement is more appropriate.