How do I get the guys to appear in Minecraft PE?

I'm posting on behalf of my 4.5 y/o son. He has Minecraft PE on the ipad and sees all these youtube videos of minecraft with actual people there. Do I have the wrong version? Does it need to be on the computer? Or does he have to be linked via WiFi to other players? How do you get an actual player/guy/person?

Please help a momma out!!

Many thanks!