Know how to write a song?

I have a school a signment for music aperaition class and it's writing a song.
So do any of you know how to write a song?

Nope.

I've only written two songs in my life so far, one had to come to me in a dream, the other came to me after a series of brainstorms, but other than that, you have to have both talent and skill to write songs, think of lyrics, come up with a tune, etc.

No, not really.

I've recorded on my computer a couple little tunes I came up with, but that's about it.

Not really - I write lyrics, but basically that is just writing down what comes to me. I've found it is best to come up with the tune and then the lyrics, but that's all the advice I can give. Write about something meaningful to yourself.