Try shutting the bottom vents half way and then use the top vent to control temp. This will help you to learn how your WSM wants to work and with more experience it will become easier. Try some different combinations and see what works best for you. Also, once you have a few cooks under your belt, the WSM will be more seasoned and you will have better temp control over time. That seasoning or "gunk" is part of what makes the WSM so great.
Also, welcome to the forum. It is a very friendly place and people here are very helpful. I know since 3 years ago I got my WSM22 and had never smoked anything before, only used my Weber Performer (kettle) and with the help of all here I have improved my game. We all are still learning and that is part of the fun. Some of the cooks by others here have encouraged me to try things I might not have otherwise. It is a lot of fun. Remember, BBQ is meant to be fun. Even when the results are otherwise, have fun.