How could you increase the potential energy of an apple you were holding?

If you're holding the apple at your waist, lift it to your mouth.

Potential energy relative to any level is proportional to its height

above that level. Increase that height, and you've increased the

potential energy.

Since energy is conserved ... it never magically appears or

disappears ... you need to tell where that extra energy for the

apple came from.

It's exactly the work you did ... the force of your muscles acting

through the distance you raised the apple ... that became the

additional potential energy that the apple gained.