All good info above.
Yes, the light indicates the coil is heating. When a sensor on the back wall, sees the programed temp, 225, the coil and light goes off. The controller is not a precise instrument. What ever the setpoint is, you will see 20° swings either direction.
Don't trust the meat probe and set your temp to a known accurate therm with the probe on the same rack as the meat. DON'T CHASE THE TEMP. Set the MES to the desired temp. Tweak to get desired temp, at meat level and be patient. We want the Average temperature to be what you want. Say 225 with 20 degree swing is Normal!
Leave the top vent open while making smoke. You want convection and fresh smoke contacting the meat.
The MES is Tight and holds moisture, most of us don't add water to the pan. Foil wrap to keep it clean. Some guys add Sand as a Heat Sink to moderate those temp swings.
Feeding Chips every 30 minutes gets old on a 16 hour overnight smoke. Get an
A-MAZE-N AMNPS Maze or
AMNTS Expandable Pellet Tube Smoke Generator. Load with pellets get it smoking, put it in the MES and get out of the weather! Also look at the Mailbox Mod, very popular.
Get some Chicken to play with until you get your smoker dialed in. Good luck and Welcome to SMF...JJ