How do I build an android apk?

I’m new here also new to ionic. I have developed a simple app using Ionic 4 -beta and firebase and its functioning well except that am unable to build a apk so that I can test it on my android phone.
How do I build one to test??

Have you read:

@ChrisGriifith, yes I have already tried to use those steps and am getting this error: (kindly check the attached)

@ChrisGriiffith, kindly assist in this, I have not yet been able to get the apk.

try running

$ ionic cordova build android --verbose

Have to removed the android platform from your project and reinstalled it?
Have you been able to run the app in the Android emulator?
Also what is your ionic info output?
Finally, have you searched these forums?