How to add Zoom webinar to my existing meeting subscription?

Hi, Gavin.

Once you login, you can check it, in the billing page at https://www.zoom.us/billing.

Kind regards,

In the navigation panel, click Meetings. Click the name of the meeting you would like to convert to a webinar. To the right of the Start and Edit buttons, click Convert this Meeting to a Webinar. Confirm that you want to convert this meeting to a webinar by clicking Convert.

Regards,
J Wick