hello leigh,
i hope you are doing good.
you can add the option by going to 'organisation settings' of your company's control hub instance, then scroll down to the simultaneous interpretation section where you will be able to activate and select the languages that will fit your needs.
in case that the section is not yet available on your control hub instance, please contact your customer success representative to have it activated: https://help.webex.com/en-US/article/WBX15/How-Do-I-Contact-My-Customer-Success-Manager-(CSM)?.
from what i know, it is a free feature.
here is an interesting article on this nice feature:
https://help.webex.com/en-US/article/o0p0l4/Simultaneous-interpretation-in-Webex-meetings-and-webinars#Cisco_Reference.dita_c3fec2eb-60ea-4823-931f-b9524d0705f4
