During a recession Fed usually tries to increase the money
supply as recession is a time period in which the Economy faces a
decline in GDP and various economic activities which is accompanied
by unemployment.
It increases the money supply by purchasing government
securities from the open markets which increases the amount of
reserves in the economy and the inflation rate.
This action of Fed decreases the interest rates as money supply
and Interest rates are inversely related to each other, thereby
increasing the overall spending in the Economy.