Can't open application from unidentified developer

I'm using macOS Sierra and I can't open an application because it's from an unidentified developer. I went into my Security and Privacy settings and clicked on "open anyway" but it still doesn't let me open the app. How do I open an app from an "unidentified developer"?

There's a terminal command for this. I don't remember using it, and never wrote it down in my Sierra tweaks file. However:

sudo spctl --master-disable

From OSXDaily: How to Allow Apps from Anywhere in macOS Sierra Gatekeeper

you can do this with terminal

sudo xattr -d com.apple.quarantine /path/to/application.app