I started off picking five teams starting a Dynasty mode. I picked Oklahoma, LSU, Ohio State, USC, and Notre Dame. I simmed the season and went with the team that was ranked #1 or #2 and received the National title invitation.
I played the title game to get the National Champions achievement.
In my simulation Sooners was the team I went with. Through the remaining two seasons, I simmed guaranteeing a winning season. I simmed by week to ensure the team was undefeated. Make sure you quick save (LS) to guarantee your team remains undefeated. Reload your dynasty if the team is beaten.
I continued this process through the 2nd season and 3rd season. I played the National title game in all 3 seasons.