That is Eclipse with the Flex Builder *plugin* installed. To
use it you just run the same old Flex installer, and select the
Eclipse plugin in the options when it asks you (instead of the
It sounds like you downloaded the SDK, and not Flex Builder.
The plugin (just like the standalone version) isn't free. You can
use the (free) SDK, which is just the library files needed to
compile a Flex app, but if you want IDE support you will either
have to wait for a free 3rd party solution or purchase Flex
Using the free Flex SDK but not Flex Builder is like coding
in Java with notepad. It's possible, but you'll probably want the
IDE tools for anything serious.