Question setting up a user group on a LAN

[ddelport]

After finishing a Access Database I placed it on a shared folder on a Network Server. I set up user accounts for the intended users but afterwards I accessed the database from another pc (To my utter Horror!)without being prompted for a user id as what I would expect. I am somewhat of a novice still and don't really have experience in the use of Access on a local area network. The setup is that every user has a copy of Access 2000 (MS Office Package)on their PC's. I want everyone to use the same database on the network folder but with the security features. Firstly to restricted access to the fragile tables and to have a log of the users in certain table fields.