Due to security reasons, Apple decided to remove “Allow apps downloaded from: Anywhere” option in macOS Sierra, but fortunately for those who are using macOS Sierra 10.12.1, you could get this option back by typing in the following sudo command line into terminal app to allow installation of apps from anywhere. Instructions are shown below.
sudo spctl –master-disable
Once in, type in this command line : sudo spctl –master-disable and hit enter.
The app will now request for our password. Type in your password, NOTE that you password will not be visible. After keying in your password, hit enter.
Thats all you need to do to get the option back.