Crock pot/slow cooker?

I am using my crock pot/slow cooker for the first time and the booklet says it works best if the crock pot is at least half full. I cut a medium onion in half and then in chunks, half a yellow pepper, half a red pepper, and half a green pepper. I am trying to make dinner for myself and three roommates. I am thawing four chicken -standard size. There are two in a pack (sorry it doesn't say the weight). My question is how much chicken broth should I add in the morning? Enough to cover the meat or should it just be an inch or so at the bottom? I was thinking it should cover the meat, but that would be A LOT of broth! Please help and please be specific...virgin college cooker over here and its too late to call mom! Thanks in advance.