how to change a file in github using simple-git npm pacakge

Question

I want to change my old file with new file using simple-git npm package but I am not able,

 
const simpleGit = require('simple-git');
const git = simpleGit(); // or git = simpleGit(workingDir);
git.init(onInit).addRemote('origin', 'git@github.com:SoorajSunkar/test.git', onRemoteAdd);
 
function onInit (err, initResult) {
    console.log('done init')
 }
function onRemoteAdd (err, addRemoteResult) { 
    git.add(['test.txt'])
}