Advent Television Problems?

I recently got an Advent Television for my room. It's the combo TV with a built in DVD player, 2 AV inputs, and 1 AV out. I'm trying to connect a Nintendo 64 to the TV, but no matter what channel I switch to, the Nintendo won't be displayed. I can't seem to find any support forums online about this sort of thing, and none of my friends even have an Advent TV. I'm completely lost... Also, it didn't come with a remote control, so I have a limited range of things I can try. With that in mind, please HELP!!