Flushing the system is needed every time the filter is changed or once the refrigerator is installed to the water supply line for the first time. The air in the water system may cause dripping at the dispenser that is considered a leak or for the water to dispense slowly.
Here is a video and instruction on how to do this:
https://producthelp.whirlpool.com/Refrigeration/Water_Filter_Information/Installation_Support/How_to_Flush_the_Water_System_in_a_Refrigerator