Two-factor authentication configuration in GitHub

Go to your profile icon (right top corner)
select setting
select account Security (available in left side)
click on Enable two-factor authentication  (scroll down you will get a button)
select set up using an app radio button
click on OK button
Download Google authenticator app from play store
click on + symbol and scan the QR code which will be available in your screen
download the recovery code and click on yes,
you have done with two-factor authentication in your GitHub account.