What is the best child internet filter software?

Hi expert,
I am a businessman. Most of the time, I have to stay out of my house. I have a son of 5 years old. He stays home and wastes his time using internet. So, I need your help. I heard about an internet filter software. But I don’t know what the best child internet filter software is and how to use it. Please, tell me in detail as I can use it.
Thanks
