Update readme in demo project

demos/example-node/README.md

@@ -2,7 +2,18 @@
 
 This demonstrates a small NodeJS client opening a database and connecting PowerSync.
 
-To get started, set up a PowerSync service instance with the default rules for the todolist examples.
-Create a development token, and use it to implement `DemoConnector.fetchCredentials` in `main.ts`.
+To get started with this example, you need a configured instance of the sync service.
+This example expects the the schema [created in this guide](https://docs.powersync.com/integration-guides/supabase-+-powersync#configuring-powersync),
+which you can follow to start a compatible service.
 
-Then, use `pnpm run start` to open a database, connect to PowerSync, wait for a first sync, and run a simple query.
+Being a simple CLI program, this currently doesn't implement authentication. So, you'll need to
+create a [development token](https://docs.powersync.com/installation/authentication-setup/development-tokens#development-tokens) to run this example.
+This demo expects the URL of the PowerSync instance in the `DEMO_ENDPOINT` environment variable,
+the development token is read from `DEMO_TOKEN`.
+
+Once you have those values ready, you can use the following command to open a database, connect to PowerSync,
+wait for a first sync and run a simple query.
+
+```
+DEMO_ENDPOINT=https://yourinstance.powersync.journeyapps.com DEMO_TOKEN=YOURTOKEN pnpm run start
+```