No worries, it is pretty simple all things considered. Your 13,000 btu will do a solid job of warming up your camper, but if you are connected to shore power it is always a good idea to supplement (and reduce LP use) with a ceramic heater.
Assuming you have an analogue thermostat all you really need to do (assuming the LP tanks are open) is switch the lever to heat and then set your desired temp.
If you have a digital thermostat it is slightly more complicated, but it is the same idea. If it is digital, please share which one it is (even a photo) and I'm sure someone here can simplify the process for you.
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