The Install New Software wizard allows you to add new software to your installation. To install new software:
Help > Install New Software.... This wizard shows you the items that are
available for installation.Some of the items may be digitally signed by the company that provides them. This allows you to verify more easily that the features and plug-ins that are about to be downloaded and installed are coming from a trusted supplier. You may be prompted to verify digitally signed content once the signature is detected.
Warning: Because of the possibility of harmful or even malicious software, you should only download software from parties that you trust.

Updating the installation
Uninstalling software
Reverting to a saved configuration