📚 clarify how this is "two npm projects"

README.md

@@ -10,13 +10,15 @@ To deploy a frontend-only React app, use the static-site optimized
 
 ## Design Points
 
-A combo of two npm projects, the backend server and the frontend UI. So there are two `package.json` configs and thereforce two places to run `npm` commands:
+A combo of two npm projects, the backend server and the frontend UI. So there are two `package.json` configs and thereforce [two places to run `npm` commands](#user-content-local-development):
 
-  1. [`package.json`](package.json) for [Node server](server/) & [Heroku deploy](https://devcenter.heroku.com/categories/deployment)
-      * `heroku-postbuild` script compiles the webpack bundle during deploy
-      * `cacheDirectories` includes `react-ui/node_modules/` to optimize build time
-  2. [`react-ui/package.json`](react-ui/package.json) for [React web UI](react-ui/)
+  1. [**Node server**](server/): [`./package.json`](package.json)
+      * [deployed automatically](https://devcenter.heroku.com/categories/deployment) via heroku/nodejs buildpack
+  2. [**React UI**](react-ui/): [`react-ui/package.json`](react-ui/package.json)
       * generated by [create-react-app](https://github.com/facebookincubator/create-react-app)
+      * deployed via build hooks in the Node server's [`./package.json`](package.json)
+        * module cache configured by `cacheDirectories`
+        * bundling via `heroku-postbuild` hook
 
 Includes a minimal [Node Cluster](https://nodejs.org/docs/latest-v8.x/api/cluster.html) [implementation](server/index.js) to parallelize the single-threaded Node process across the available CPU cores.
 
@@ -81,7 +83,12 @@ If an app was previously deployed with [create-react-app-buildpack](https://gith
 
 ## Local Development
 
-### Run the API Server
+Because this app is made of two npm projects, there are two places to run `npm` commands:
+
+1. **Node API server** at the root `./`
+1. **React UI** in `react-ui/` directory.
+
+### Run the API server
 
 In a terminal:
 
@@ -93,6 +100,12 @@ npm install
 npm start
 ```
 
+#### Install new npm packages for Node
+
+```bash
+npm install package-name --save
+```
+
 
 ### Run the React UI
 
@@ -110,3 +123,12 @@ npm install
 # Start the server
 npm start
 ```
+
+#### Install new npm packages for React UI
+
+```bash
+# Always change directory, first
+cd react-ui/
+
+npm install package-name --save
+```