from http://flex.apache.org/doc-getstarted.html
Run the SDK installer. The first question you will be asked is the installation directory.
/Applications/Adobe Flash Builder 4.7/sdks/4.14.0/
C:\Program Files(x86)\Adobe Flash Builder 4.7\sdks\4.14.0
You will need to create the 4.14.0 folders. Press Next. Accept SDK Licenses and Install.
IDE Specific Instructions for Apache Flex setup: