Without telling us what you do not understand and what info you got/checked already, it is hard to help you.
Just providing example code won't help you to learn it then
You new WINDOW_MANAGER:CreateControl to create your CT_BUTTON control. And at best use a "fragment" as the parent of the button which will be added to the HUD and HUD_UI scenes so that the fragment hides/shows as you show the menus, or the ingame world:
https://wiki.esoui.com/Fragments_in_...t_state_change