How emails will be sent to candidates who are not in system for Campaigns or Events?

Summary:

how emails will be sent to candidates who are not in system for Campaigns or Events? Or is there any HDL/HSDL to load to create candidate to add in the system and then add in the campaign or events?

Content (please ensure you mask any confidential information):

Version (include the version you are using, if applicable):

Code Snippet (add any code snippets that support your topic, if applicable):