A key part of the setup on my site is SSL, Certbot from LetsEncrypt makes the whole process incredibly easy, and it all runs on our favourite computer the Raspberry Pi.
Pre-requisite for this is Nginx installed and a domain name pointing to the machine you're installing it on
First you need to install certbot on your Pi
sudo apt-get install certbot python-certbot-nginx
Then just run it
sudo certbot --nginx
This will validate your site and DNS file and if they correspond you will have a nice shiny new cert installed et voila!
There are more variations on this involving Docker that Humankode has documented superbly Docker and Certbot on Nginx