The fed can attempt to increase the federal funds rate by

selling Treasury bills, which decreases bank reserves.

Explanation:

The federal government on attempt to increase the federal funds can decide on selling treasury bills.

When the treasury bill is sold, it will affect bank reserves, the effect it will have on bank reserve will lead to decrement on the bank reserves.

Once there is a decrement in the bank reserve, after the treasury bill has been sold, this will lead to an increase on the federal funds.