You may need to go to System Settings > Privacy & Security and click "Open Anyway" if macOS blocks the installation because it's from a third-party developer. 3. A Note on Adobe Flash Player
If you are trying to download software for a 3D printer: Download Flash mac txt
Open TextEdit (found in your Applications folder). Go to Format > Make Plain Text to ensure it saves as a .txt file. You may need to go to System Settings