1. Download the SDK from http://www.adobe.com/products/flex/flexdownloads/

(click on the “I have read the Adobe Flex 3 SDK License” checkbox, and the download link will appear below)

2. Use stuffit expander / unzip to uncompress the archive.

3. Open the terminal (if not open already), and go to the folder where you uncompressed the archive to.

4. Type the following:

sudo cp -r flex_sdk_3 /Developer/SDKs/

5. Edit your ~/.bash_login to include the following line:

export PATH="/Developer/SDKs/flex_sdk_3/bin:$PATH"/

This will add the binaries to the path. If this file doesn’t exist yet, go ahead and create one. Next, create a new terminal window to have the right binaries in your path.

6. Try it out. Create a file named “helloworld.mxml” and paste the following into it.

Make sure there is no whitespace before the XML declaration 7. Try it out. Go back to your terminal and type (from the directory where helloworld.mxml is) type the following:

mxmlc helloworld.mxml

This will compile the file using the Flex 3 SDK. It should create a file in the same directory called “helloworld.swf”.

8. Open up helloworld.swf in Firefox. If you have Flash 9 installed, it will show you your compiled Flex application!