Tae Kwon Do is a year round sport with no seasons or sign in days. The easiest way to get started is to speak to your local instructor and let them know of your interest in starting Tae Kwon Do. When you come along to your first class, wear comfortable clothes that you can move around freely in. Your first lesson is free and you are under no obligation to join.
If you decide that Tae Kwon Do is right for you or your family, your instructor will give you the rest of the basic information at the end of the lesson. Buying a uniform is not something you have to do straight away, but it will be required before your first grading. Any other equipment you will eventually require can be purchased when needed.