First of all: If you share a content item (here is a guide), Authory will NOT push the share link to Google for indexing.
However, if you share the link somewhere and Google "sees" this link, it will still go to the link and index the page. If you want to make sure that will never happen, you can disallow Google (and any other search engine) from indexing your piece like this:
Go to the respective content item in your Authory account.
Click "Settings" in the top bar.
Switch on the toggle labelled "Disable search engine indexing"
Please note that you'll only find the toggle in the Settings menu for items where the share link has been enabled.