Click Computer management > system tools > shared folders > Shares or if u want to see which user is connected to comp click computer management > system tools > shared folders > sessions even u can see what shared files r opened now, follow the same steps as above just change open files instead of sessions. It is best to define a group policy for that issue. For this, click computer configuration > policies > windows settings > security settings > local policies > audit policy > audit object access, here u check define these…. settings” & again check success and failure boxes. If u feel this is a long process / face probs, then simply use ShareWatch which helps u lot and free
Be sure to enable auditing only when you really need it, and only on the objects you really need to monitor. Audit logs can grow really fast.