You didn't tell us but we are assuming the bike has a Chinese 2 stroke engine. If so the clutch lever must be depressed (squeezed) when the bike slows below about 10 mph. Many people today have never driven or operated a motor vehicle with a manual transmission and clutch. It isn't the same as an automatic transmission.
If he is squeezing the clutch lever but the clutch isn't disengaging correctly then he has a clutch adjustment issue. Let us know and we can offer details on how that is done.