Can't play the music downloaded onto my mobile through Spotify.

[Wexton]

I go to local files on spotify on my desktop and it shows everything in "My music" folder. 

I hook up my mobile to my computer, copy and paste all the music files into my SD card.

I open up the spotify app on my mobile

I can not play my music the same way I could on my desktop from "local files" 

They just don't show up or I don't know how to use the mobile app.

I want all my music, not just the playlists I made that I can apparently download from my account or whatever. (idk that's the only result I found when I tried to search the problem)