Click on the orange square, keep the mouse button down and drag it to the blue square, release the mouse over the blue square.

REGIONS ARE NOT ENABLED
between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares between the squares
after the squares after the squares after the squares after the squares after the squares after the squares after the squares after the squares after the squares after the squares after the squares after the squares