How to Download and Install Lion Server Components from the App Store
If you have installed the Lion client on your hardware and are ready to upgrade to Lion server, you need to download and install some Mac OS X Server software from the Mac App Store. Follow these steps to convert a Lion client to Lion Server:
Launch the App Store from the Dock and log in with your (or your organization’s) Apple ID.
Purchase Mac OS X Server or if you’ve already purchased it, go to the Purchases icon in the toolbar and click the Install button.
After a short download, another installer launches, displaying Welcome to Server.
Click Continue in the Welcome to Server window and then click Agree to the Software License.
Click Continue in the Install Software window.
At this point, the installer begins to download server software.
Enter the Mac’s local administrator name and password
In the Configuring Services window that appears after the download and installation of software is complete, click Finish.
The Server app opens, with the Next Steps pane expanded at the bottom. Lion Server is installed and ready for configuration.