The answer to 'how to unclog sump pump' is to first unplug the pump and remove any debris or obstructions blocking the inlet. Next, use a wet/dry shop vacuum to suction out any standing water in the sump pit. If the pump still does not turn on or clear the water, you may need to disassemble the pump to clean or replace the impeller.
It's important to take safety precautions when working with electrical equipment and standing water. Wear rubber gloves and boots, and turn off power to the pump at the circuit breaker before starting any repairs. If you're not comfortable doing the work yourself, it's best to call a professional plumber who can properly diagnose and fix the issue.