To set up Saved Replies, please look at this article.
Once your Saved Replies have been set up, you can then use them in one-to-one communications with Applicants.
To do so:
Inside the Application, click on the triple dots menu and click "send email"
On the Content Editor, click the document icon.
From the dialog box that appears you can search for the reply you want. Click the check button to select it, and "Use in my reply" to add it to the email you're writing.