The Setup Panel is the 'last' panel in the event panel menu, but the one you'll go to first when setting up your event.
Here's where you create and define the settings that will customize your event. This includes your brand (the 'look and feel' of your event), payment types and taxes, overall preferences, and the set up for each "module" [Registrations, Functions, Presentations, etc.].
So this is where you create and edit Registration Types, Marketing Tags, Travel sectors, Sponsorship packages and more, all ready to be applied throughout your event.
Why do some users see Lock/Unlock symbols on modules?
If you're seeing these, then you have Administrator rights, or have been given permission to lock areas of the Setup Panel.
Once locked, other users cannot change anything in these areas (unless they have been given the same permissions). This can help stop inexperienced users making unwanted changes.
There are three sections in the Setup panel - click each link to learn more.
System Setup [your Event system setup]
Event [This is where you can add modules if needed, under the Modules tab]
Module Setup
This is where you'll set up each module. You may not see all those modules in your event, and/or you may not use all of them.