Everyone was a beginner at sometime and learning about electricity pays dividends when you can look after it yourself. There is plenty of good information that can be had on this site as well as the rest of the inter web. One page that you will find referred to often is the "12 volt side of life", lots of really good information there.
Start by checking the fuses, your distribution panel should have one or more fuses that look about 2-3 times bigger than the regular branch circuit fuses. Also look for a battery disconnect switch, on the older rigs, many of them came with them from the factory and are usually close the the distribution panel.
Use either a test light or multimeter to check for power on both sides of the fuse, don't rely on a visual inspection, fuses can loo OK, but the filament could be broken.
If you don't have a multimeter I would suggest that you get one, you will need it somewhere down the road.
The key to successfully diagnosing a problem in your 12V system is to start at the beginning of the circuit and follow it all the way to the end.
