The most basic procedure for installing Papyrus consists in installing the Eclipse Modeling Package for your own platform.
Then, you have to use the discovery interface ("Help" => "Install Modeling Component") and select Papyrus.
Proceed through installation steps. Once the installation is completed, you will be asked to restart your eclipse platform and then Papyrus is ready to use!
Papyrus Update Sites
Eclipse provides also facilities for adding new software to the platform or updating software in the system.
In all cases, the site location (i.e. the Web URL or the archived Update Site provided above) is the only required item to update or install a software within Eclipse.