How do I add a custom taxonomy as an option for menus under “Appearance” > “Menus”

I’ve created a custom taxonomy and I want to add it as an option for custom menus (under Appearance > Menus). How do I get it to show up there (see the illustration, I want it to show up where the red square is).

Your custom taxonomy should show up as an option for custom menus, if you have

'show_in_nav_menus' => true

as a parameter when you register your post type with register_post_type(). You can check all the available parameters in the codex entry http://codex.wordpress.org/Function_Reference/register_post_type#Arguments