How to trim the sail with the two cleats?

Cunningham

Sail with a loose cunningham in light wind. This gives power to the sail. When the wind picks up, tighten the cunningham to flatten the sail.

Vang

When sailing upwind the vang is not useful. It should be lightly tightened downwind, just enough to prevent the sail from going upwind.

When the wind picks up, it is helpful to take the vang upwind to ease the strain on the sheet.