Speak to your adviser. This is the person that helps you register for classes and guides you towards graduation in your program. Explain the reasons that you would like to take a year off of school. You don't have to be approved, but you must follow certain steps to make sure you won't have to reapply when you wish to come back.
Contact the registrar and fill out the paperwork to request a leave of absence from school. If you don't get this paperwork completed, you will be considered to have dropped out of school, and you will need to reapply and be accepted when you come back.
File the paperwork with the registrar and with your adviser or program chair. It is important that these people understand what you are doing and that you will be returning. Stay in communication with both parties so that you can return to school more easily.
Contact the registrar's office in plenty of time before you return, so that you can register for classes and not fall behind.