Easiest way will be to do it as follows:
- Shut down nginx
- Install discourse per official install guide
discourse/docs/INSTALL-cloud.md at main · discourse/discourse · GitHub
- Follow other sites on same server tutorial to create a server block in nginx to forward requests to Discourse and modify the yml to use sockets.
Add an offline page to display when Discourse is rebuilding or starting up
The above link should give you a good starting point
- Rebuild discourse with new configuration
- Start nginx