i need help

na it can't be that, they have vids on their channel lolz i'm thinkin they might mean how to put a vid in your signature but i'm not sure :L
when someone open my channel , the video will be running ..
Oh yeah my bad :p

So you mean when some one goes on your channel, it starts auto-playing?

At the top of the vid it should say edit (on the channel) Click that and tick automatically start playing then save :)