I’d recommend starting with Michael Mosely’s book, or at least reading the guidance on this site. There is a get started tab at the top.
find yourself a good app online for counting calories and carbs (myfitnesspal is good, I use fitbit, there are others)
cut out all junk food, and bread, potatoes, pasta, rice. Avoid starchy fruit like bananas and limit the other fruits as they all have sugar and carbs, a few berries with full fat yoghurt is ok.
Use full fat products where possible if you are having yoghurt etc as this makes you feel fuller.
Have a good browse of the recipe threads here and look elsewhere online for recipe ideas. If you like to bake I’d recommend trying some of the alternative flours available, Almond flour is amazing, and coconut flour is good as well.
A typical day for me is yoghurt and fruit for breakfast, then either soup or (homemade with almond flour) crackers with cheese and salad for lunch, and a fairly normal meal most nights just without the starchy carbs. Try courgetti, and cauliflower rice instead of pasta and rice.
The important thing about where and how to start really is to just get to the shops, buy what you will need for the next few days, get rid of the stuff in the house you know you need to avoid (if you can- I have people in the house who eat them) and then just do it. Don’t wait too long because once you get started you will regret waiting!
Read the forums, lots of motivational stuff in here.
Best of luck to you 🙂