To be certified you have to take the Apple Logic Pro Certification exam, via an authorized Apple training center. The exam is based on the official Logic training book (by David Nahmani, Peachpit Press). You could also take the course based on the book, again, at an authorized Apple training center—I believe it's a three-day course—but if you already know Logic well, you don't need to take the course ($$$$), you could just study the book. Btw, even if you do know Logic well, It's still recommended that you study the book—everybody works their own way in Logic, but the certification exam is based specifically on the way things are described and presented in the book. There is an Exam Preparation Guide with practice questions, though apparently the questions on the exam are not drawn directly from it.