From a copyright perspective, a song needs to be “fixed” in some medium in order to qualify for protection. In reality, this means it must be either written down or recorded, and preferably both. If you just sing and play the song in a room it doesn’t qualify for protection, so it is important to at least get a decent recording of it.
You can have a musician transcribe it if you want to have it written down, too. I realize this may not be your most urgent consideration when you start, but it is important and worth knowing from the beginning how you will protect your song once you’ve created it. Getting a recording and having it written down are key to that. Recordings can be made cheaply and easily today, and for the writing part, having the melody, lyrics, and chords notated is enough.
Can anyone write a song?
Almost anyone can write a song, but that doesn’t mean it will be a good, or lasting one. Having a career as a Songwriter requires daily practice, study, and work. Professional Songwriters sometimes work in teams, or co-write with other musicians. To get a few successful songs, it might take writing a few hundred. It’s easy to see why not too many people can actually have lasting success as a songwriter.
Not everyone wants to write songs as a career, though, and it’s fair to say that you could make a good song when just starting out, provided you have a bit of talent, and good luck. If making music and songs interests you, then it’s time to get busy! Learn all you can about the process of song-making.
Fortunately, there’re excellent resources for this, as can be found on this website and others. You can learn a lot from reading the articles and then doing additional research on your own. And it might not hurt to take a few music lessons along the way. There are even some music teachers who specialize in teaching Songwriting techniques.