Q: Why won't my Apple TV connect with my mac computer or iPhone?

I have a macbook pro and an  iPhone 5. Not sure which generation my apple TV is but all I know is that while I was at home I was apple to do things like mirroring what was on my computer or phone screen on to the TV and playing the music from my phone and computer onto the TV. Now that I'm at school, I can't seem to get any of this to work. I followed all set up instructions and even made sure that the apple TV is connected to the same wifi network as my phone and computer. I followed some trouble shooting guides but they seemed to be a little outdated. I have home sharing turned on on all of my devices. I am also kind of slow when it comes to these kinds of things so please talk to me at like a 5th grade level lol thanks in advance!