How to involve multiple annotators

Hello,

This project looks very amazing~ I am a newbie and have no previous experience in developing web pages. I am marked blocked by multiple annotators. I have successfully deployed locally, but I don't know where to get the external domain name in https://labelstud.io/guide/start.html#Run-Label-Studio-with-an-external-domain-name.
Thanks a lot~

Best,
Xinyi