bitnami subdomain has been indexed by Google

Hi,

I installed wordpress on bitnami, and I got a subdomain

xxxx.bitnamiapp.com

This url has been indexed by Google, how can I stop Google from doing this?

Currently I am using this subdomain to build the website, once finished the work, I will use my own domain. I know that I can do something in robot.txt file, but I want to make sure that it will not block Google indexing my own domain

So I only want to block the subdomain indexing, how?

Thanks