14 and 263 pounds. Advice? I'm very overweight for my age and need some advice?

Something you might want to know is that there's a possibility I have low thyroid levels and I'm gonna be seeing a doctor about it soon. Okay so I do and don't want to start exercising. The problem is I don't know what is the best exercises. I'm gonna be honest. I'm pretty poor. Not poor like some ppl say yet they have iPhones and nice cars and stuff. No I live in a trailer and stuff but anyways what i'm saying is that I can't afford to go join a gym or anything. But on the bright side I do have a mile long trail near where I live that I can walk on. All together it would be two miles there and back and I find it easier to walk a mile on that trail than a road. But is that all I need to do everyday I mean it is two miles. I'm going to start eating healthy too. But besides the two miles is there anything else I should do? I want to loose at least 138 pounds

One kid I know lost a ton of weight by not drinking anything with sugar in it.
No cokes, no juice, nothing. Just water and plain tea.
Add that thought?

Start with the sugar. Thats a good idea. Not even diet soda. Your body still processes diet soda as sugar. Take a walk every day after dinner, go a little longer every day. Is it possible to go to the gym? I'm a firm believer in cardio and weight lifting to shed pounds a build muscle.

Cut down on soda sugar drinks, chips fast food. Go on daily walks at least 30 min a day Cut down on portion of food its a great start. DRINK LOTS OF WATER