Hi Rolando -
Learning to read music and writing songs are two separate things, though reading music will certainly help you writing songs.
Do you play guitar, or piano? A good way to get started writing music is to learn how to play a simple song that you like, and change it in little ways -- change the words, change the tune around.. just try different things and see what sounds good to you.
When you know more about reading music and how music works, you'll understand better why some things sound good and some don't... that's one reason why learning to read music and understand it is important. Another reason is that when you can't figure out how to play a song on your own, you can just read the music and play it right away! (It does take some time and a lot of practice to learn it, though...)
The best way to learn to read music is to work with a teacher, but if you are on your own you can start out at some of the websites listed here:
links to learning websites
Good luck, and if you have specific questions you can always ask them here!
-Rob