Jet pumps only have to be primed once. After this initial priming, they should automatically prime themselves whenever necessary. However, if you have never primed a jet pump, you need to know how to do it this first time. As long as the foot valve or check valve is fine and there's no air leak on the suction side of the pump, this will be the only time that you will have to go through this process.

...
Prime a Jet Water Pump
...

Step 1

Locate the priming plug on your pump (see picture).

Step 2

Unfasten the plug.

Step 3

Fill the pump with water. Both the pump and suction pipe should be filled.

Step 4

Re-insert the priming plug. The plug should only be fastened loosely at this stage. Later, it will be placed more securely in the opening.

Step 5

Turn on the pump. Water should begin pumping within 20 seconds.

Step 6

Tighten the priming plug so that it won't come undone while the pump is running.