Only one person can go on the lift at a time, it's all you need.

You can only plant two pieces of fruit (besides the first one you get given anyway at the start of the game), after the second piece they just deposit the fruit in the food bin.

Leave the person on the lift when it rains and watch the lift rise up. Then you'll see a piece of fruit fall down - then just get your villager to pick it up and plant it (Don't disturb them while their planting!)

The trees take a while to grow though!