Welcome!
Just head on over the the New Mystery Shoppers area and read the first dozen or so topics that are "pinned" to the top of the list. That will explain most of what you need to know so that you can get started. Then, after reading, head to any of the areas to post questions and go to the bottom of the page to see the list of legitimate Mystery Shopping Companies (MSCs) that you can start to sign up with.
Based in MD, near DC
Shopping from the Carolinas to New York
Have video cam; will travel
Poor customer service? Don't get mad; get video.