Order a catalog of master's degree courses from individual universities. This will provide more detail than simply browsing online and will provide you with contacts for the next step.
Think about your practical skills, previous work experience and other educational qualifications you have achieved. All of these things go in to shaping what could be the right master's degree course for you.
Discuss the potential of applying for a master's degree with appropriate sources. This could include the boss at a relevant workplace (they may very well have gone through this process to get where they are) or tutors at a previous educational institution.
Phone the university of your choice and ask them about the course. You need to find out the specific qualifications needed, the cost and whether you could gain any additional experience which could help you get into the course.
Apply for the master's degree course and school of your choice, using the methods outlined by the particular school. Make sure you have appropriate funding; like regular university courses, master's degrees, although shorter, are still costly.