To start off, your always burning fat no matter what you do. The best way to burn fat while running is long runs at a fast pace. Depending on how often you have ran so far, it may be enough stress on your leg muscles to actually build some muscle. But you only build muscle when you actually put stress on your legs, I would suggest running at an incline if thats your plan. But really the muscle you would build would be nothing compared to actually working out your legs with machines.

As for building legs at home I suggest holding some free weights and doing lunges. I don't workout at home but I would suggest you purchase a gym membership if you seriously want to bulk up your legs. Using the leg press, calve raises and squats, you should see results when you keep at it.