This AWS deployment guide is brilliant. Thank you so much for putting it together.
I’d recommend following this for instructions on installing and configuring nginx and this for configuring the certificate (just skip the apache stuff and adapt to nginx):
sudo add-apt-repository ppa:certbot/certbot
sudo apt update
sudo apt install certbot python-certbot-nginx
sudo certbot --nginx
crontab -e
@daily /usr/bin/certbot renew >> /var/log/letsencrypt-renew.log
sudo service cron reload