Use their guide of downloading the Niners99 roster or any team's 99 overall roster that you can use and start an ONLINE CONNECTED FRANCHISE and create either a coach or owner (player should work too but I have not seen a guide to confirm that). Then, import the roster, and change the difficulty to ALL-MADDEN and turn SALARY CAP off and turn all the CPU settings on.
Here is a video walkthrough:
Credit to 🐧 titansfreak28 🐧