Safety first keep the key out of the ignition.
Shut power off and air released from brakes wheels blocked.
sharing how I replace engine fan belt. recommend replacing alternator belt also because need to remove fan belt to install alternator belt.
regular tools used- 3/8 flex head long ratchet (helps with keeping tentioner down to align belt) and add deep socket with extension for leverage while holding it down with one hand and adjusting with other