To install additional components, you can run the installer again. The installer detects the newly-installed components and uses them to satisfy the dependencies of other components. Installed components are disabled at the Component Selection page.
For example, suppose you have installed Access Manager and its required components during this installation. Later, you decide to install Portal Server. The existing instance of Access Manager will be used to meet the Portal Server dependency on Access Manager. You will not be asked to reinstall Access Manager.