I have Execution environment references were not checked for '...' because no environment descriptions are installed. error.

I guess I need to install environment descriptions (http://wiki.eclipse.org/Execution_Environment_Descriptions) for the org.eclipse.jdt.core project that causes this error.
How can I install environment descriptions in eclipse?
I got an answer from this site – http://wiki.eclipse.org/Execution_Environments#Installing_Execution_Environment_Descriptions
In short, you can install software for Execution Environment Descriptor.
to remove the error.