taking audio from a video for iPhone ringtone...

i came across a video clip on twitter and was trying to do some research to see if i could take the short audio (around 7 seconds) and turn it into a ringtone for my iPhone. i did come across an article saying i could use the Quicktime Player so i tried it with my macbook pro, but, i am not having any luck with that. it could easily be i am doing something wrong. i am wondering if anyone could help me with this---if it can be done at all. thanks.