Starting with Mac Sierra, Apple made it more difficult for users to download and run many of their favorite apps.|
By default, the Download from Anywhere radio button is hidden from the Security & Privacy panel on System Preferences. Users are sometimes confused and searching for help to simply add an App to their computer.
With AllowApps, click a button to restore the Anywhere option. If you later change your mind, click Restrict to hide it again.
See how to Install AllowApps on Catalina.