Find some introductory tickets (also shown below) that have the "Ready for Work" status to work on, and assign them to yourself by clicking the "Claim Issue" button. (Ask for clarification on the ticket if needed.)
Click "Request Code Review" and a core developer will get you some feedback in short order
Find another ticket or choose a larger project to work on. See Unassigned Projects.
If you join a sprint or choose to share your module (we hope you do), then you'll want to read about how to obtain committer subversion access if the ticket you wish to work on resides in the SVN repository.