Flex Compiler Problem

Hi All

I'm new to Intellij Idea as a Flex IDE, so i am just having a look around and testing.  I have created a test app, edited the configuration file, but when i go to run the app, i get a message and pop up box appear saying ' Main Class For Module ...... '

So what do i do now ?

Also, code hinting assist seems very slugish, is there a way to speed this up ?

Many Thanks

Whitetimer