i just recently had to do this myself, since i was on exec board i sat down and spoke to my president about it and we filled out the paperwork. later i sent out an email to the chapter explaining why and telling them how much i'd miss them, we held a goodbye dinner before i left

i don't know if you're transferring to a school that has your chapter or not, but i did not and it has definitely been one of the hardest things i've ever down. i was obviously super involved and attached to my chapter and suddenly not having that has been difficult