Q: how do you subsribe to itune

You don't subscribe to iTunes itself (you can just buy whichever songs/albums/films etc that are available in your country's store), or do you mean iTunes Match (which isn't available in all countries) ?

About iTunes : http://www.apple.com/itunes/

iTunes match : http://www.apple.com/itunes/itunes-match/

subscribing to iTunes match : http://support.apple.com/kb/HT4914