Start with the chords

Chords are what help people sing the song. You could be missing everything else, but chords, and you can sing a song. So start your music creation process by laying out the chords. Chords for pretty much every song you have heard are on the internet, so get them, and use the tools of your music software to construct them. Use an instrument that sounds good with chords.

Add a melody

The melody does not necessarily accompany the entire song, but it's good to have. It's very hard to write a melody, unless you have very trained ears. But you can add short melody progressions throughout the song instead. Use another instrument, or several other instruments. Use notes that are present in the key your chords are in, so a song would sound right to the western ear. If you don't know which notes go with which key, you can just use the same notes present in your chords, but arrange them in different order and lengths.

Add bass line

Bass line uses an instrument that sounds like a bass guitar. And it uses the lowest notes of the chords. So copy the chord progression you made when creating chords, and leave just the lowest note of each chord. Then, break up those notes into patterns, instead of having just one continuous note.

Add drums

Once you have the melodic and harmonic structure of the song, experiment with creating simple drum patterns using the drum sounds in your music software, or drum loops. Once you have a drum loop created, copy it, and make slight variations to the loop, so that the drums don't sound the same for the entire song.

Build from the chorus and to other parts

Chorus is the most exciting part of the song. Start by building the structure for the chorus. Than copy the entire block from chorus and rearrange it to create verses, intro, outro, intermissions... Verses should have less sounds, and be less exciting, to allow the listener to listen to the words of the song. At the end of the verses, you build up to the chorus, using things like drum rolls and pitch changes. Intro should be interesting, but not too complicated, just so the listener keeps listening to the song.

Add bells and whistles

Add sound effects and other things to make your song more interesting and unique.

Mix and master

Mix your instruments like a sound technician mixes a band before performance. Assign low sounding instruments (like a bass guitar) to lower frequencies. Assign high sounding instruments (like high hats) to higher frequencies. Highlight the main frequencies of an instrument. When you do that for all instruments, you will have a fuller sound, with all instruments occupying their own place, rather than interfering with each other.

After that, you would ideally give the track to a mastering specialist, who has the right equipment and experience to make sure the track sounds good on any type of speakers. Or, if you're like most people, who can't afford a specialist, you'd have to do it yourself. Test how it sounds in different places, on large speakers, in headphones, in the car; and keep adjusting until the track sounds balanced, not squeaking, not coughing, and all sounds can be heard as intended, on different speakers.