The listings of available of assignments is in the left-hand column of your main page on iSS. Login to your account on iSS and look in the left hand column for Available Shops. This is where you will see all of the jobs that shoppers can select. Also, there is another selection, Web and Phone Shops, where you see those kind of shops.
Hope that helps. Happy shopping.
P.S. If you have not signed any MSP contracts yet, then you cannot pick any jobs. Each one has a contract that you must sign in order to pick an assignment for them.