How do I send a song from my computer to another computer?:)

You could e-mail it or save it to a disc or memory stick then transfer it.

You can embed music/song in an e-mail with OE if you want, can be annoying sometimes. DavidB
Embedding Music into Email - WorldStart Computer Tips and Computer Help

Use a USB flash drive to copy it from one PC or another. It's the simplest and easiest way.