Create a new workspace for your Eclipse RAP projects. As you have to change the target platform to compile against Eclipse RAP your existing projects may not work with the RAP target platform

Download the "Eclipse for RCP and RAP Developers" from the Eclipse download site . This download contains the RAP tooling.

Eclipse RAP have its own target platform. A target platform contains the artifacts, e.g. plugins, against which the Eclipse plugins are compiled. For example Eclipse RAP does not rely on SWT but on RWT therefore the target platform must provide these.

Download the RAP target platform from Eclipse RAP downloads and unzip it into a new directory, e.g. "c:\EclipseRAPTarget".

Change the target platform under Window -> Preferences -> Plug-in Development -> Target Platform

Press "Add".

Select "Nothing" as template and maintain the directory of the target platform as the location.

Switch to your new Target Platform.