You will have to sideload it. First enable "unknown sources from "settings/security/". Then proceed to download it from Adobe flash archive. Make sure you choose the last (highest number) version for Android. (Scroll down a bit). Unless somethings' changed, the right link reads: "Flash Player 11.1 for Android 4.0 (11.1.115.81)"
Once it is downloaded, you may have, depending on your browser, have to launch the APK manually. It will be in your "Downloads" folder. Further more, it has to be enable in the Browser's settings. Not all browsers allow this anymore. Dolphin browser does.