How to download the ssl certificates?

Hello World! I recently moved to the squarespace. I have a website hosted on google cloud in a compute engine virtual machine. I am using nginx as the webserver. I wanted a domain name and ssl certification for my site, therefore I chose squarespace. I managed to redirect the http requests to the server. However I can't still set up nginx with https as I don't have ssl certificates downloaded in the server. I sought everywhere, but found nothing on how to do so. Anyone have a solution for this?