Installation with Homebrew
brew install nginx installs Nginx and a default configuration that listens on port 8080 (not 80), so it can run without root. Start it as a service with brew services start nginx, then browse http://localhost:8080.
Configuration
The main file is /opt/homebrew/etc/nginx/nginx.conf (Apple Silicon; /usr/local/etc on Intel). Add per-site files under /opt/homebrew/etc/nginx/servers. Validate with nginx -t, then nginx -s reload.
Serving on port 80
To listen on the standard HTTP port, change listen 8080; to listen 80; and start Nginx with elevated privileges (sudo nginx), since ports below 1024 require root.