I’ve finally gotten around to documenting how to activate the Hawaiian keyboard in Windows 10. It is included in the linked PDF document below. I have not had the opportunity to do this for Windows 8 or Windows 9, but the process for those versions should be similar enough that anyone with Windows should be able to figure it out. As always, please note I don’t provide personal tech support for any of the documentation on this website.
Directions on how to type the ‘okina and kahakō using this keyboard are on the second page. Also please note that not all Windows fonts have the vowel/kahakō combinations and the ‘okina.