How the FOMC affects interest rates
The FOMC uses the open market operations of the Fed as the tool to change interest rates.
Open market operations can tighten or loosen the money supply. If the Fed wanted to tighten the money supply, it would offer government securities for sale. Institutions would exchange cash for government securities. If it wanted to increase the money supply, it would buy securities, pumping cash into the financial system.
A tighter money supply means it’s harder to borrow, and interest rates rise. A looser money supply means it’s easier to borrow, and interest rates decline.
Although the FOMC sets a target interest rate, banks actually set the rates. It’s up to the open market operations of the Fed to adjust the money supply to the point where the rates naturally fall within its target range.