After enabling a SPF record for the domain, you can configure it by going to Email Deliverability in cPanel » Manage » (SPF) Customize.
In the "Current “SPF” (TXT) Record" field you can view the record which is currently enabled for the domain.
In the "Suggested “SPF” (TXT) Record" field you can view an exemplary record, which is automatically generated by cPanel and it contains all recommended parameters.
To add more servers authenticated to send messages from your domain, you need to edit the existing SPF record. You do not need to add a second SPF record for the domain.
Additional IP Address Blocks (IPv4 / IPv6)
If you have the IP address of the outgoing mail server for the domain, you can add the IP in the Additional IP Address Blocks (IPv4 / Ipv6) field.
Include List (INCLUDE)
If you are sending emails through Google and Outlook, you can add Google and MS mail servers as authenticated to send emails for your domain by adding them to the Include List (INCLUDE):
Preview of the Updated Record
After the changes are performed on the record settings, an exemplary SPF record will be generated in the field "Preview of the Updated Record”. Before saving the changes, you can check the exemplary record. You cannot perform changes on this field's record as this is a preview of the record's final version.
Save the record changes by clicking on Install a customized SPF record.
Configuring a SPF record through Zone Editor in cPanel
If you already have a SPF record, you can set it for the domain in cPanel » Zone Editor » Manage (for the domain) » TXT – Add TXT Record.
You can also change the whole SPF record in cPanel » Zone Editor » Manage (for the domain) » TXT (the record containing SPF) - Edit.