Typically all you have to do is log into your 401k plan's website and access your account. The website should have a section where they give you the forms to fill out and/or the request form should be available. You might also need to contact your HR department for the proper forms and/or contact information about who to contact about loans from the 401k. Some plans do not allow loans, so you need to be aware in case yours doesn't. Also some plans have different third party administrators who handle the loan compliance so it is always good to speak with HR and/or the person who set up the plan at your office.