I had a similar smoker, also from Masterbuilt, but it was propane. And I now have a charcoal vertical smoker/grill, but it's a kamado so it's a bit different. That said, I've read enough that I might be able to offer some thoughts.
I would recommend looking at a lot of the information, tips & tricks, etc from the Weber Smoky Mountain (WSM) cookers. There's differences, but both the WSM and your cooker are vertical metal cookers. Being charcoal, the tips on how to build your fire will transfer -- look up the
minion method in particular.
The biggest issue with a smoker like this will be keeping the door airtight. These are regulated by airflow, so leaky doors mean that you'll have trouble controlling airflow with just the vents. You need to use some sort of heat-tolerant seal on the door to avoid that. When I had my Masterbuilt, I just bought a fireplace gasket and it did the trick.
Since it's vertical, it's key to have some sort of a baffle to protect the food from the direct heat of the fire. It looks like it has a water pan. Some people use water (or other liquid) in that pan, which is totally acceptable. Some people prefer a more dry environment and just fill it with sand. In the Masterbuilt, I typically used a water pan, and the food came out great. In my kamado, I use a ceramic heat deflector, and the food comes out great. But either way, you definitely want to block that direct heat or you'll end up scorching the bottom of whatever you're cooking. You also may want to adjust the shelves when you're cooking to try to keep food as far away from that fire as possible, to avoid scorching.
Remember that the thermometer on the door is useless. A good electronic thermometer that clips onto the grates will give you more accurate information.
And of course your first step is burning it hot (400 F+) without food to burn off any manufacturing oils, then to burn it with cooking oil smeared around the inside to help season it.
I'd recommend the first few burns, like brewbama suggests, be very "forgiving" meats like sausage, pork butt, ribs, etc. Take the time to learn how your smoker reacts over time to both the upper and lower vent settings changing, so that you don't try to put a brisket on for a party and have a fire go out overnight or something similar. Consider it to be "research"... Tell SWMBO that you absolutely
need to spend all day out there with some homebrew watching the smoker
Enjoy!
