First confirm that the water is available by turning off the water and disconnecting the hose at the washing machine. Put the hose into the washer and turn the water back on. Good pressure? If so the problem is in the washer. If not, you may need a plumber. You can disconnect at the faucet end and see if there is a screen in the hose that is plugged, but usually not. If it's the washer, you will find a screen in the water valve right where the hose attaches. Is it plugged? If so, clean it. If not you will probably have to replace the water valve on the washer.

What appliance is this?