Eclipse is probably best known as a Java IDE, but it is more: it is an IDE framework, a tools framework, an open source project, a community, an eco-system, and a foundation.https://www.eclipse.org/eclipse.org-common/themes/solstice/public/images/logo/eclipse-200x200.png
There are several different ways to add a new update site to the list of sites available from the Install Manager. In all cases, the site location (i.e. the Web URL or the archived Update Site provided above) is the only required item.
To add the MoDisco site, one of the procedures described from the Install Manager documentation must be followed.