You can just copy-paste the whole code into your own app.js file.

"Slack Example" app.js

/*
* Advanced Cloud Code Example
*/

var express = require('express');
var app = express();

// This will be our route handler for the /unbilled Slash Command
app.post('/getUnbilledUsers', async function(req, res) {
    const query = new Parse.Query(Parse.User);
    query.equalTo('billed', false); // find all unbilled users

    let unbilled;
    try {
        //.find() returns a Promise so we can await it
        unbilled = await query.find();
    } catch (e) {
        res.status(403);
        res.send({
            text: 'An Error occured'
        });
        console.error('Error' + e.message);
        return;
    }

    if (unbilled.length === 0) {
        // If there are no unbilled users, send a different response
        res.send({
            text: 'No unbilled users!'
        });
        return;
    }

    // If there are unbilled users, format them and send them as a response
    const usernames = unbilled
        .map(user => {
            return `Username: ${user.get('username')} | User ID: ${user.id}`;
        })
        .join('\n');

    res.send({
        text: 'Unbilled Users:',
        attachments: [
            {
                text: usernames
            }
        ]
    });
    console.error('Error' + e.message);
});

//This will be our route handler for the /bill Slash Command
app.post('/billUser', async (req, res) => {
    const unbilled = await new Parse.Query(Parse.User)
        .equalTo('billed', false)
        .find();

    for (let user of unbilled) {
        try {
            await user.save({ billed: true }, { useMasterKey: true });
        } catch (e) {
            res.status(403);
            res.send({ error: `failed to bill user ${user.id}: ${e.message}` });
            return;
        }
    }

    res.send({ text: `${unbilled.length} users successfully billed!` });
});
/*
* Exporting of module.exports.app is required.
* we mount it automaticaly to the Parse Server Deployment.
*/

module.exports = app