Changing the Lenses:
You will see a black plastic piece above the nose bridge. This piece holds the lenses in place. You will need to turn this piece vertically and wiggle it out to remove it. Then, you can insert a different lens and replace the black piece.
Replacing the temples/strap:
Squeeze the rectangle in. If it doesn't feel like it's moving in, take a key or a coin and press gently to help it loosen up. Make sure not to bend the temples when removing them. As you're pressing the rectangle, wiggle the temple left to right gently to loosen it up and off.