run your test pages against browserstack first by installing to cli globally

npm install -g run-browserstack-tests

then create a config json file

{
    "username": "BROWSERSTACK_USERNAME",
    "key": "BROWSERSTACK_KEY",
    "test_path": "PATH_TO_HTML"
}

then simply point run-browserstack-tests to your config

run-browserstack-tests -c PATH_TO_CONFIG

the module will take care of getting to the html from there.

a full command has to have a query parameter passed to it. A perfect example is the following

run-browserstack-tests -c ~/Sites/config.json -q "~iphone"

or without the config all together

run-browserstack-tests -u BROWSERSTACK_USERNAME -k BROWSERSTACK_KEY -f TEST_PATH -q "~iphone"