Edit the setting.json and modify:
"requireAuthorization": true,
Uncomment
  "users": {
    "admin": {
      "password": "changeme1",
      "is_admin": true
    },
    "user": {
      "password": "changeme1",
      "is_admin": false
    }
  },
Edit the nginx config file and add:
proxy_redirect         / /pad/;
after
proxy_pass             http://localhost:9001/;
Restart nginx and etherpadlite.
Acces to admin panel at /admin
But, the admin panel is empty…
I have an nginx error:
2015/05/29 00:03:03 [error] 8390#0: *517 connect() failed (111: Connection refused) while connecting to upstream, client: 192.168.1.67, server: crudelis-test.fr, request: "GET /pad/static/js/l10n.js HTTP/1.1", upstream: "http://[::1]:9001/static/js/l10n.js", host: "crudelis-test.fr", referrer: "https://crudelis-test.fr/pad/"