First of all,you are advised to master an instrument if you want to start composing songs.Piano and guitar are the two instruments that i highly recommend you to learn as they really useful in your song composing.Next.I’m gonna guide you step by step how to compose a complete song.
This is the song composing route map that you must bear in mind if you want to compose a complete song. idea > inspiration > find a suitable chord > use a simple sequence of song first if you just a newbie to music composing <intro-verse-bridge-chorus-bridge2>,dun worry,this will be discuss in later chapter>refine the song till you satisfy >constructing the background music <this require technical and experience> >advertise your song to your friend or profession >ask comment from them >refine >a song is completed.