If I understand correctly you wish to block all search engine bots from your site? If you Q2A site is in the root (e.g. example.com/) then put the following in a file robots.txt at example.com/robots.txt
User-agent: *
Disallow: /
If your Q2A site is in a subfolder (e.g. example.com/qaname/) then you would need to put /qaname/ next to disallow, instead of /