Download the C4J Plugin
This plug-in is written with Java 1.5 and therefore you have to run Eclipse with a 1.5 compliant java runtime.
Eclipse Update Site
The preferred way to download the plug-in is via the Eclipse update manager. Under Help > Software Updates > Find and Install... chosse Search for new features to install and click next. Then choose New Remote Site... and enter as URL
http://c4jplugin.sourceforge.net/update
Click Finish and go through the dialog which follows.
You don't have to install the runtime plug-in separately. It is available from the same update site and will get installed automatically.
Direct Download
Alternatively, you can download the plug-in from the location below. In order to install it, just copy it into the plugins directory of your Eclipse installation.
net.sourceforge.c4jplugin_0.1.1.jar
This plug-in depends on the plug-in net.sourceforge.c4jplugin.runtime. You can get it here.