My 2004 hybrid was a manual light. Just look outside (most likely in the back) for a vented door, that hwh should be behind that. The directions should be on a plate in plain view. You basically turn a black button to the on/lite position then push straight down to release the propane. You'll need a grill lighter to reach the thermocouple. Oh heck, this is too much work, just watch this
This is for a suburban hot water heater. Atwood will be similar, I think the valve to light it will be a little different.