Database connection FPS game?

I have a database with users and a FPS game.. i would to connect the users in the database with the unity game to make a online multiplayer game.. but i don't know what i have to do... i think i need a login form... i need smarfox server?? please don't ask me to buy photon cloud.

please, if you have a guide or a tutorial, answer me please help me

sorry for my bad english because i'm italian!