There is no "right" or "wrong" way to the process of writing a songs.
It varies greatly from song to song and from band to band which approach is used.
Usually the way I have done it was to come up with the music first and then some fitting lyrics, but it happens sometimes it is the other way around or they come up more or less simultaneous.
I've been in a band where the usual approach was to build up the songs around my bass lines I arranged to fit together almost as a base to a finished song, and then as we went along changed the arrangement a bit, added some riffs and put drums and guitar on top of that.
I've also been in a band where the songs were build up around the gutarist/singers more or less finished songs (chords, riffs and vocals), and finally I've been in a band where one of us would come with one or a couple of riffs we presented at rehearsal and then the others would add their stuff on top of that and contribute to the song with additional riffs that fitted into the initial ones and then lastly everyone would contribute to arrange it into an actual finished song.
In the current electronic music project I am in, songs usually starts with one of us laying down a drum track and a bass line, then we take turns in putting down additional tracks, until the song is almost finished, then I record additional non electronic and progammable instrumental tracks down on top of that, and finally we come up with some lyrics and record the vocals.
Anyway welcome to the exiting world of song writing and good luck
