How to treat fingernail fungus?

I been wearing acrylic nails alot for several months now. I have just recently had a set taken of and I was left with one discoloured nail which kinda freaked me out. I have been to my doctors over this. She told me it is nail fungus. I have never had any kind of fungus before and i'm kinda freaked out over it. She has gave me Amorolfine Hydrochloride Nail Lacquer to treat it but i'm not exactly sure how to use this. As anyone had nail fungus before and if they have how is it treated. Does Amorolfine Hydrochloride Nail Lacquer work and how do you apply it. Do I put it on every nail or just the one infected nail. Be grateful if my questions could be answered.