Launch Flex Builder 3 and go to Help>Software Updates>Find and install…
Check the Search for new features to installoption and click Next
Now create a New Remote Site…
Visit the Subclipse website’s install page and note the latest release’s update URL; it should look something like this:http://subclipse./update_1.6.x.
Enter the URL found at the site above and give the update site a name; such as Subclipse 1.6.x and click OK. Then ensure the new remote site is checked and click Finish.
Browse the Subclipse tree to find the Subclipse plug-in items; i.e. Subclipse 1.6>Subclipse