to store Important Data into a PC

hI THERE,

i JUST connected one pc to the network. We have our domain here.Configured tcp/ip/assigned ip/mask/dns. Everything is there.I also mapped some drives on this pc.Now , I need to allow some users to store some important data in, and allow some users to share the info for each other as well. I dont know how to configure the next as new IT guy here.Please advice.