The Send Emails tool acts as a bridge between your inbox and the FindThatLead automation platform.
That said, you should not configure any settings other than connecting the account via SMTP / IMAP.
DKIM and SPF records should have been configured before you start sending emails.
Having your DKIM and SPF records configured correctly is crucial to ensure a good domain and email reputation.
Here are helpful resources on how to configure your DKIM and SPF records based on your email provider.