LTS-5452: README step to set credentials as env vars

README.md

@@ -6,11 +6,33 @@ This repo contains samples for running [Nightwatch](https://nightwatchjs.org/) t
 ## Setup
 
 * Clone the repo `git clone https://github.com/browserstack/browserstack-nightwatch-load-testing-sample.git`.
-* Set `BROWSERSTACK_USERNAME` and `BROWSERSTACK_ACCESS_KEY` as environment variables with your [BrowserStack Username and Access Key](https://www.browserstack.com/accounts/settings) 
+* Set your credentials as environment variables, as described in [Set your credentials](#set-your-credentials).
 * Use Node.js 20 or later. For the seven-day release-age policy in `.npmrc`, also use npm 11.10 or later (`npm install -g npm@11.10.0`, which needs Node.js 20.17+ or 22.9+); older npm ignores that policy.
 * Run `npm i` to install the dependencies.
 * Open the browserstack-load.yml file and update it with the relevant load test configurations.
 
+## Set your credentials
+
+The BrowserStack CLI reads your credentials from environment variables. Copy your username and access key from [Account Settings](https://www.browserstack.com/accounts/settings) and export them in the shell you run the test from:
+
+On macOS or Linux (bash or zsh), run the lines below. The second one prompts for the key without echoing it, so the key stays out of your shell history:
+
+```sh
+export BROWSERSTACK_USERNAME="<your-username>"
+printf 'BrowserStack access key: '; read -rs BROWSERSTACK_ACCESS_KEY; echo; export BROWSERSTACK_ACCESS_KEY
+```
+
+On Windows, run these in PowerShell. The second line prompts for the key in the same way:
+
+```powershell
+$env:BROWSERSTACK_USERNAME = "<your-username>"
+$env:BROWSERSTACK_ACCESS_KEY = [System.Net.NetworkCredential]::new('', (Read-Host -AsSecureString 'BrowserStack access key')).Password
+```
+
+These variables last only for the current terminal session. If the CLI reports an authentication error, check that both are set in the terminal you run it from.
+
+**Never commit your credentials.** Keep your access key out of `browserstack-load.yml` and every other file you push. If a key is ever exposed, regenerate it from Account Settings.
+
 ## Running your tests
 
 - Download the BrowserStack CLI for your operating system. The download is a zip: extract it and place the `browserstack-cli` binary (`browserstack-cli.exe` on Windows) in the root of this project. On macOS or Linux, also run `chmod +x browserstack-cli`, since some unzip tools drop the executable bit.