A good project starts with a good idea: one that addresses a real need, is feasible and well-scoped, and isn't well covered by existing open source projects. (Before you create a new project, we suggest that you try searching for existing projects on this site and elsewhere on the web. You can often get further faster by helping out with an existing project than by starting one from scratch.)
If you're ready to start your own project, you'll need to write a description of it and give it a good name. Then, sign in using a Gmail account, enter that information into the Create a project page, and you're done. Congrats. You've got a brand-new project on Google Code.