Welcome to the forum, marvathibou. There are a lot of mystery shoppers, and many shoppers face a lot of competition for a limited number of shopping assignments in their area. The most time-consuming part of MSing is researching and building and maintaining a MS client list. Many shoppers invest a significant amount of time in this research, so their lists are valuable. Most do not share their lists with others who live in their area, because it then increases the already-stiff competition.
Visit the new shopper area for how-tos and register with at least 50-100 of the companies in the list at the bottom of the page. Many of us are registered with 150 or 200. Check out Jobslinger for some companies in your area. Plan to work hard and spend a lot of time getting started and getting your list set up.