Good Morning!
First, understand that this is an open forum where mystery shoppers can share their experiences and help one another. This is not an actual mystery shopping company. That said, you are in the right place to get yourself started. Everything you need to be know can be found here.
1. There is a "New Shoppers" area on this forum. Read the pinned items - there is a huge amount of information about the mystery shopping world there.
2. Linked at the bottom of this page is a list of over 200 legitimate mystery shopping companies. Start with the "15 Most Discussed" as they are larger companies with shops all over. Register yourself with one at a time and check their job boards. If you really get into this, you will find yourself registered with well over 100 companies.
3. When you see a shop on a job board that you want, request it through the job board. When you get an email notifying you that you have been assigned, read the guidelines, follow them, do your report online, and get paid several weeks later.
This is not hard. However, it is a bit tedious, especially at first while you are spending a lot of time signing up for new companies. As you have questions, feel free to post them here. You are almost certain to get a myriad of responses.
Good Luck and Welcome!
Hard work builds character and homework is good for your soul.