Step-by-step SSL for Node JS / Express Application

I assume you already have an Express server that looks something like this:

Install Certbot onto the machine that your website is hosted on:

Certbot

Have two terminals open to the machine hosting the website.

1. For handling the Certbot instructions.
2. For editing your server file.

On your first terminal run the command:

certbot certonly --manual
/* OR */
sudo certbot certonly --manual

Next, you will be prompted to enter your domain name:

<YOUR_URL>.com www.<YOUR_URL>.com

Then something like this should pop up:

Create a file containing just this data:
<RANDOM_STRING>
And make it available on your web server at this URL:
http://<YOUR_URL>/.well-known/acme-challenge/<RANDOM_STRING>