You'll have to assign the users you want to allow access to to a group. Click Start>Settings>Control Panel, then Administrative Tools. In Computer Management navigate to System Tools>Local Users and Groups>Users. In the details pane right-click the user then select Properties. Select the Member of tab and click Add. Select the group you want to add the user account to, click Add and then OK.
In Computer Management, select System Tools>Shared Folders>Shares, then click Action>New File Share. From the wizard select eh files you want to share and set the permissions. You can do this by right-clicking the folder whose permissions you want to share, and then selecting Properties.
Think I covered everything.
