How to open app from unidentified developer?

Here is a more graphical overview of the dialogs that you can receive when initially opening the document from a control-click to verify the developer. If the developer is notarized, then it is as simple as opening that app, watching the verification progress bar, and then clicking Open on the subsequent dialog. If the developer is not notarized, then it becomes a multiple choice problem based on the dialog that you receive from the first Open.

Find the app in your Applications folder. The control-click on it and then click on "Open" from the context menu.

Open a Mac app from an unidentified developer - Apple Support