A pump is not very effective at pumping air, so you will need to prime the pipe between the pump and the check valve located at the well head, just above the vertical pipe connected to the sand point. Suggest locating the priming port on the pressure (outlet) side of the pump, as that will prevent any potential air leakage caused by a poor seal around the priming port since it will be on the pressure side of the pump whenever the pump is operating.
Once the pipe is filled with water, activating the pump with a faucet open, will then cause the pump to pump out the water from the pipe, which will in turn create a vacuum on the check valve which will then draw out the air from below the check valve. Drawing the air toward the pump will then cause the vertical pipe below the check valve to become filled with ground water that enters through the sand point.
Depending on the amount of air below the check valve, and the distance between the pump and well head, once that air arrives at the pump, the pump may loose prime once again, so you may need to re-prime,. The amount of additional priming water should be relatively small, only to replace the air that had been below the check valve. Because the vertical pipe below the check valve will then continue to remain filled with ground water since the check valve will have prevented the vertical line from draining, the pump should continue to supply water without interruption after the re-prime.
