Before you can organise a Teams Live Event, you will have to request for your Office 365 licence to include the Teams Live Event policy - please raise a Help Desk ticket.
Once you have been informed from IT that the licence has been enabled, please give at least a further 48 hours before you will be able to set up a Live Event.
Teams live events is an extension of Teams meetings, enabling users to broadcast video and meeting content to a large online audience. It is managed in a very different way to Teams Meetings.
These resources are current to todays date (18/03/2022). Please note Microsoft Teams is a evolving application.
Within the How to Teams Live Event, there are some very useful links, please watch.
It is important before running a live event, you practice and get familiar with the production of this type of event, it is very different to a Teams Meeting.