This proverb means you can show someone the way but cannot force anyone to follow it. Let's understand by taking an example, If somebody asked you about your opinion about something, you can only give him your opinion, you can't make him accept your opinion. You can just tell him what to do, you can't make him follow the right way or the way you like. It is his choice to choose the way. God always shows us the way but is is upon us if we decide to choose the right path.