To book the IELTS exam, visit the official website of the British Council, IDP Education, or Cambridge Assessment English, which are the three main IELTS test providers. Create an account, select your preferred test date and location, and pay the exam fee online. Make sure to provide valid identification details as required. Upon successful payment, you'll receive a confirmation email with further instructions for the exam day. Be sure to prepare well for the test to achieve your desired score.