Go to a club, find the hottest chick in the room.
Hit on her, note the look of disgust and burn it into your mind.
Every time you think of having biscuits or coke or **** in the future, remember that look, remember it alongside how you feel looking in a mirror, and put them down, and drink water and chew gum.
Make your bed, every single morning. Sounds trivial, it starts a routine that'll give you the tiniest bit of order that will help do everything else.
Go on Amazon and buy 20kg of dumbells, start low, build them up. Do it 5/7 Days a week. Even if it's only 20/30 curls and shoulder rows.
Ice Cold showers morning and night, horrific at first, but activates brown fat (that burns calories by itself just for existing) and gives you a cold water resistance that's life-saving if ever you fall in a river.
Drink water. All the time. Every single thing you drink, make it water (or a diet protein shake if you really take off on the lifting)
Download Couch to 5k. Once you start building muscle and have confidence, go out running. I go at 6am, nobody is about, nobody can't run, and that running program is take the piss easy to get you running to 5k if you follow it.
Within 4 months you will have hit all your goals.
I was 26 stone when I started doing this, I'm 19 stone now. I started in March.