First take this link from youtube http://www.youtube.com/watch?v=IytNBm8WA1c
Then take these numbers and symbols
IytNBm8WA1c
add [.youtube] at the beginning and [./youtube] at the end and you end up with this. (remove the "."s)
when you make a post there is an own button for this which looks like this
this will provide you with the tags you need at both sides.
Also please read the rules before posting in the next time, tutorials is not the place to ask questions.