@HannumR
If you want to add and remove them for the whole recurring series:
On your org.webex.com site click on Meetings > then click on any of the upcoming weekly standing meetings > at the right-hand side you can add an attendee, to remove one click on the ellipsis (...) next to their email address and select remove. . If you are only looking to have someone in as a one-off or delete someone for a certain week then for a weekly meeting
If you want to add and remove them for individual occurrences in the series (i.e. make it an exception to the series):
On your org.webex.com site click on Meetings > then click on the meeting in the series you wish to change > now click on the pen/pencil edit icon
then select Edit only this meeting > make your change(s) and Save.
When you now look at the upcoming meetings you will notice the recurrence icon next to the meeting title has a line through it to indicate the meeting is an exception to the recurrence.
Hopefully this help you out.