Typically, you package the war file using 'ant' or 'maven' tools.
While you are picking up those tools, you can do the following::
Right click on the war file, i.e 'jbpm-gwt-console-server.war', and open using 'WINZIP' and add the jar file.
But you need to add the jar file into WEB-INF/lib first. So create a folder WEB-INF/lib and copy the jar file into WEB-INF/lib directory, then right click on 'WEB-INF/lib' and move to the war file.