Simple and fast: Create a sandbox game with unlimited money.
Next hold LT and press B button, then youll find the edicts screen. Just start selecting them, you'll know they are active because it will appear a little red star.
You can scroll between 4 screens with buttons LB and RB.
Note that not all the edicts will be available because some need you to build something, but it doesn't matter, you will have more than 20 available without them.