There is a script available on every cPanel servers by default to enable the SPF and DKIM records via command line.  This will surely help when there is a need of adding the records for many accounts at the same time.

If the SPF is only for a single account, do it like the following:

# /usr/local/cpanel/bin/spf_installer $username

Do not forget to replace $username with the actual cPanel username.

If the DKIM is only for a single account, do it like the following:

# /usr/local/cpanel/bin/dkim_keys_install $username

Replace $username with the actual cPanel username.

These commands will help you to enable email authentications for single cPanel users. If you have many accounts and you want to enable SPF and DKIM for all accounts, please follow the simple for loop.