Question 1: did you use a metal screwdriver to adjust the pots while the printer was powered on?
Question 2: did you see where the flame came out of? Was it the stepper driver or something else?
Without seeing the damage it's difficult to help. You could have destroyed the driver, RAMPS, or the arduino board itself. Try troubleshooting incrementally. Make sure everything is powered off. Then connect the arduino via USB and check if it connects to your printing software. If not, the arduino is likely damaged and needs replacement.
If the arduino responds, try powering the machine on and jogging the axes. If all axes but one move, you must have damaged the stepper driver for that axis. It needs replacing.
If the axes don't move at all, you either burned all the drivers at once or damaged the Ramps board. Most likely the only fix is to replace all the damaged components.