1) Get a faculty sponsor at your school.
2) Get multiple other adult sponsors who can help you and chaperone you on trips. Likely these will just be parents of members (or other faculty). There are going to just be some things that you can't do without adults, such as book a bus or book hotel rooms, or even rent skis without waivers and other legal related stuff.
2) There should be some guidelines somewhere at school on what you need to form a student group. If not, get in touch with another successful student group and see how they set things up.
2) Figure out what your purpose of the club is going to be. Whether it's just trips or other ski related stuff (like learn how to tune skis, watch ski movies, etc).
3) Explain what your club organization roles and duties (president, vp, treasurer, etc). As well as fees and costs.
4) Get members.
5) Schedule some meetings, both to plan what you want to do, and plan some trips. Have an agenda for each meeting.