i would love it if i could mirror my desktop to my tv and choose from the screen what i want to watch

i have a chromecast that's just out of the box. i am trying to stream my movies that are on my desktop computer. some reason, nothing seems to be working. can anyone point me to a link that works the best? or give me some sort of step by step instruction that would allow me to stream to my vizio tv, my ipad, etc? i just want to be able to stream itunes movies to my tv as well as my downloaded videos that are sort of old.