I have a description how to install Egit on Eclipse on a client.
According to the description I have done the following:
.) started Eclipse
.) selected Help -> Install New Software ...
.) In "Work with:" selected "--All Available Sites--"
.) in the filter field entered "egit"
Nothing to select appears as the client is obviously not connected to the site.
There might be the following solution, but I could not try it up to now:
.) Get the addressof the site with the software.
.) If this can be used in the "Add ..." function, I might have done.
.) Otherwise I perhaps can download the software to a local directory and use this directory an the "Add ..." function.