Question

Explain how to use the reserve requirement to

expand the money supply.

Short answer

A lower reserve requirement increases the money multiplier and immediately creates excess reserves.

Step-by-step solution

Concept Preface 

Bank's Reserve Demand
The reserve demand is principally the defined chance of a bank's deposits which it's bound to maintain with the central bank as either deposit or cash in its vault.

:Explanation of Solution

The most critical concern of the Federal Reserve is to maintain a safe and stable public financial system. To achieve this thing the'Fed'has created a reserve demand for all banks. It also makes small changes in the reserve conditions nearly every time. As per the policy, the banks are needed to hold a certain chance of reserves.
Incase Fed increases the banks' reserve conditions, the banks will haveless money available to advance out, which means reduction in money force. Vice versa, if the Fed would reduce the reserverequirement it'll automatically increase the money force in request. Principally, a lower reserve demand increases the money multiplier and incontinently creates redundant reserves.