How to lose 100lbs in ~1 year?

Im a senior in highschool and at 17 yrs old, 5ft 9, i weight ~280lbs. Im taking a gap year after i graduate in 4 months and ill be working about full time, in that year i want to make a lot of changes to myself, my weight being one of them.

If anyone could give some advice as to how to go about this and how i could start now it would he great.

The reason im this overweight i guess is because ive generally lived a very sedentary life, i want to change that but im not sure how to exactly, and while im not extremely anxious, its quite a bit scary to show up at a gym or start walking round the neighbourhood even though i know nobody cares.

Im aware of all the basics, CICO, dont start with too much of a deficit, dont rely on motivation and discipline instead, dont fall for fad diets. I got all this knowledge from trying and failing over the years, but i can never apply it for over a month. Most weight ive ever lost is around 10lbs.

Ive tried almost everything in the past but been unsuccesful, i think im gonna start counting calories again tommorow.