It's not a one time thing... and there's nothing you have to do to access them other than play.
For normal ranked rounds you should see a mix of old & new pins... you just don't know which you will see where. The same holds true for practice rounds ... you can choose Easy, Med, Or Hard pins, but you would still see a random mix.
For unlimited tournaments, the pin set you see in your first round will be the same pin set throughout the tournament.