Exclude from search engine - robots.txt?

Exclude from search engine - robots.txt?

Hi,
 
My Support Center Plus customer portal has been indexed by a search engine, so I wish to either create a robots.txt file to stop this from happening, or to edit the meta of the main page to include "noindex".
 
Please can you tell me where the main HTTP root directory is for SCP so I can add my robots.txt file please?
 
Thanks.
 
Keith.

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