This is a wide question. I take it that MSW is a Master of Social Work, e.g. like this http://www.uni.edu/csbs/socialwo....All UN jobs are advertised on their website - UN Careers. For professional posts, i.e. those called P-1 through P-5; the educational requirement is generally a Masters degree from a reputable university (included on the list of recognized institutions by UNESCO - UNESCO Portal to Recognized Higher Education Institutions) within a field that is applicable for the post.Typically the job description will list law, economics, social sciences etc as required field of study. So, if it says Social Sciences, my guess would be that a MSW could be accepted.You can apply by identifying the jobs at the UN page above and click apply. You need to fill out an application form that can be re-used for later applications.A word of advise, only apply for jobs that you qualify for, e.g. if it says 7 years experience and you have 5, your application will be discarded.