First you have to earn 60 medals in Festival mode to unlock all areas of the playground which will unlock
Then go to the playground and on the left side of the skate park, which is in the back from where you spawn in, drive up the ramp and into the red basketball hoop. It will say "Great Hoop" if you did it right. Then go to the right side of the skate park and down to enter the basketball court. I would switch cars to the orange and white car here in the basketball area as it's much faster. Then get a running start up the long ramp on the right side of the basketball court and land yourself in the red hoop. It may take you a couple tries and you might need to experiment when speed to get it just right. I found it to be most consistent going full gas at the circle in the center of the court. I also found the Dynamic camera (change with
) to be the best for lining myself up.
Once you have gone through both hoops in the same session, the trophy will unlock.