message: Add npm login instructions
diff: @@ -24,6 +24,14 @@ The source code is organized according to where it can run:
  * **Node**: an installation of the latest security patch of Node 8.9.x downloaded from [nodejs.org](https://nodejs.org/en/). The Node installation also includes the **npm** package manager.
  * **Visual Studio Code**: an optional dependency, but the repository structure is optimized for use with [Code](https://code.visualstudio.com/).
  +## Authentication
  +
  +Configure npm and log in to the Bentley npm registry with the following commands:
  +```
  +npm config set @bentley:registry https://npm.bentley.com/npm/npm/
  +npm login --scope=@bentley
  +```
  +
  ## Build Instructions
  1. Pull repository: `git pull`
  