You will connect to Browserstack real devices using Appium URL(http://username:Access key@hub-cloud.browserstack.com/wd/hub) and App ID, I think same way will work for Simulators also
You will find Username and Access key in browserstack Summary Page
Thank you for your help, but still miss a parameter(app value of browserstack), it seems that need to upload the app to the server and get the value. but I found no upload function for getting the app value