IP Ranges

My email address is through Zoho Mail.  I have configured in Microsoft Outlook.  I have been getting alot of "Undelivered Mail Returned to Sender".  

Zoho said to resolve the issue, is to "contact your external provider support and get the IP ranges from which they trigger emails.  Add the IP address range in your existing SPF record of your Domain - [EDITED per Community Guidelines]

This would resolve your issue and you can receive emails without any issue.

How do I do this?