Visit the website of the Graduate Management Admissions Council at www.mba.com. There, you can create a user-profile and choose a test-date. You can also purchase the primary materials to start your training. However, we caution you to research more carefully about how to use these materials. In our conversations with students, we have learned of many who have exhausted the high-quality, official questions before reaching their target scores. For your own safety in the matter, so that you know the landscape, we have collected three important thoughts that every beginner ought to know here: Starting Out with the GMAT.
Exam Fee: The charge for any one sitting of the test is $250. It is non-refundable, and there are fees attached to making any of the several changes that students find they want to make. Therefore it is advisable to carefully read the policy here before booking the test date. In particular you should know a good approximation of your score before booking a test date.
Cancelation Policy: you may see your actual score before deciding whether to accept it. Other issues to do with cancelling and re-instating scores are thoroughly discussed here.