staging site /settings

good morning question for testing the set up spfcf and cf on a staging site to experiment.
which settings to use?

in the spfcf plugin i can only choose one web domain.
in cf do i need to add the subdomain with a rule or are subdomains just covered because they are under the main domain. its a different website off course so. I need to get the staging set up to work in order to properly be able to test things out.

many thanks!