This is easy. From the main menu select “Single Player,” then “Play User Generated Levels.” You can choose between “Highest Ranked” and “Most Recent” – pick whatever you like and start the level. Once it has begun, you can just press and select “Vote for Creator.” You can quit the level afterward; there’s no need to complete the level. Do this for 5 different user levels and the trophy is yours.
You can also check out the Boosting Thread if you’re feeling altruistic and do the trophy while helping others on the I Made This! trophy.