I used to work with Flex a lot. If you want to make an Android app, create a new project in Flash builder, but select a mobile app. You can then simply copy the code files from your desktop project (Adobe AIR i assume) into the the new mobile project. You should be then able to either use an emulator, or plugin an android device and test/debug directly on your device.
You might need to remove some of the controls temporarily, because not all controls have mobile theme implementation (which is used by default on mobile project, because its performance optimized), but you can build the UI relatively quickly in the mobile theme.
The other thing is, if it makes sense to use this platform anyway, since its being discontinued. Actually... donated to opensource, but we all know Flash/Flex have little future now.
Also, despite i used a relatively powerful phone at the time (galaxy s2), the application felt laggy/choppy. A lot of effort has to be put into optimization if you want to achieve native app like performance.