How add email from outlook and link/associate/add to existing candidate or client record?

How can I add an email from a candidate or client contact and then associate it with an existing record to avoid making duplicates? It seems I can only associate an email with a job. I just tried adding a candidate email (for existing candidate in my Zoho) and selected parse content thinking it would associate based on email address - NOOOO - it created a whole new candidate record. There must be something I am missing.