As soon as the match starts, go outside the ring, grab a weapon, get on the apron, go in, and when he/she comes toward you, hit them. Go back on the apron, wait until they go to the middle of the ring, and go back in and repeat until they start falling down from the shots. You will most likely be able to make them tap out with a submission. If not, beat them up a little more.
Win the championship in each federation to unlock more wrestlers.
At the main menu, press L + R + Y to unlock all wrestlers and get 300 points for create-a-wrestler mode. If you entered the code correctly, you will hear a noise.