Go to a lawyers office to write one.
You can write a video will if you need. Some poorer folks do this just before their parents die to record their will… I’ve seen some court cases where this is valid.
Just a note about folks with older parents who plan to give a will to their children... just remember that there is an inheritance tax that occurs which is about 50% of what you give. The smart thing to do is make a living will where you sign over all your property to the party you want, but you still own the property until the day of your death where then the items will be given to whoever with no tax penalty.
Interesting question though: why are you worried about what will happen after you death at such a young age? I mean most young folks have zippo to give. I have life insurance for accidental death written to my parents, but I don't plan on dying anytime soon.