Man, why's this so heavily downvoted? dude was just asking a question...
I've only used linux and android Soulseek clients, as such I'm not 100% sure for your platform, but with the ones I use, you add a directory (not a single file, but a whole folder) and whatever is within that directory is available to anyone else using soulseek
From a quick bit of googling, this may be the way of sharing folders:
Go to the options tab, click on file sharing then share folder, add the folder want to share, press ok and rescan the folder.