There is an online vacation form located on the NPL website: http://www.npl.washington.edu/r_travelform (standard CENPA authentication required). Use this form to enter, in advance, absences from the lab that aren't on official business (such as vacations or leaves). Your name, email and leave dates are required so that people looking at the vacation list can tell that you are absent (and when).
Your contract or offer letter should indicate how much vacation time you are entitled to.