The NBA Finals is a 7-game series where whoever wins becomes the NBA Champions for that particular season. The first team to win 4 games will be crowned NBA Champions. MVP is the Most Valuable Player
Now you do not have to be MVP for the whole season just for the NBA Finals. Scoring points, Rebounding, getting Assists, getting Steals/Blocks will all help you out.
You can either play all 4 games and win them getting one player as many points, rebound, assists as you can. Or you can create a player and have his stats all the way at 99. Either way you should easily get this achievement.