Q: OS X version 10.6.8 how to access Macintosh HD

"Macintosh HD" is the default name for the OS X hard disk volume, but it's far from the only name used for that. 

That disk volume name can be changed, in other words.

On various systems, you'll find your mounted disk volumes shown on the Desktop.  This includes Macintosh HD, or whatever it's been called on the local system.  Alternatively, open Finder and look for the devices in the left column; in what's called the Finder sidebar.  Alternatively, Applications > Utilities > Disk Utility can be used to show the devices present.

If you don't see the disks on the Desktop or in Finder, then you can enable and show various devices in the sidebar using Finder's Preferences > Sidebar, and you can also display the devices on the desktop using Finder's Preferences > General.

Though this is the OS X Server forum, I'm going to guess you're not using that software here.  If you're really on OS X Server and not on OS X client, then things here can potentially work a little differently.  OS X Server brings a number of capabilities to OS X client including AFP and SMB file servers, a mail server, DNS, iChat server and a variety of other services, and is managed through Server Admin.app tool, and can set up various shares that other OS X client systems access.