Most aspects of a project can be configured in the Project Properties dialog. The dialog is accessible via the Project | Properties... menu item, or by right-clicking the project in Project Explorer and choosing Properties from the context menu.
An important Eclipse concept is that a project may reference other projects in the workspace; project references can be configured in the Project References page of the properties dialog. To update the list of referenced projects, simply check those projects in the list that your project depends on, then click Apply. Note that circular references are not allowed (i.e. the dependency graph must be a tree).
In the OMNeT++ IDE, all NED types, C++ code and build artifacts (executables, libraries) in a project are available to other projects that reference the given project.
Note
To see an example of project references, check thequeuenet and queueinglib example projects.
In this example, queuenet references queueinglib. Queuinglib provides simple
modules (NED files, and a prebuilt shared library that contains the code of the simple modules),
and makes those modules available to queuenet that contains simulations (networks and ini files)
built from them.