Instead of manually editing the configuration files for WCF projects VS 2010 provides “WCF Service Configuration Editor”. Go to tools and open the WCF Service Configuration Editor as displayed below
Using this you can add a new WCF config file or open the existing WCF config file.
You can also do the same by right clicking the config file as displayed below, how ever the “Edit WCF Configuration” option will not be there in the context menu for the first time. Only after you open this from Tools as described above this tool gets associated with the config and then will appear in the context menu.