First, you have to actually share the drive like you do in win98. The default shares do not work (with the $ signs in them), you have to create a new share.
After that, go to the Users & Passwords in the control panel. Check the user must enter password and name box. This will allow you to add users. Click add user. For username enter the name of the computer on the network that you want to allow access, the other 2 fields can be left blank, then just follow the prompts for the rest of the stuff.