To get started with an initiative you'll first need a topic and a vague idea of the steps necessary to achieve your goals. With that in hand, you then search for like-minded people who have time and interest in working together on your topic. Once you have your team, you and your team sit down together (virtual or otherwise) and iron out the details of your topic idea — who's responsible for reporting, what are your goals and milestones and how does the timeline look like. Use the "initiative template" to write it down.
Now it's time to make things official: With all the details put together you can put in a request for an official initiative by contacting Benni (the TYPO3 Project Lead) — make sure to send him the completed template. Benni and you will discuss next steps and further process. When everything is said and done, you'll get your own shiny initiative page on this very website — once it's online you are all set to start working on your goals.