Burning calories to lose weight

My fiance is 245 pounds she has a gazelle that holds up to 250 pounds whats the best thing she can and fastest way she can tone muscle and burn fat tissue let me know thank you

There's no really fast way to burn fat.
The best way to burn calories is having a well-balanced diet and to excersize everyday.
Seeing progress is different for every body.
It make take a couple weeks or months.

Good luck!

Run/walk for 3-5x a week and an hour each session...Doing it in the morning whenever you wake up will increase your metabolic rate for the entire day as well as a wake up call for the body.

Of course diet is the key though.