How do I create a create a checkbox when creating a Custom Taxonomy

Hi.

This is from the docs:
"If you’ve used taxonomy field type, you will see it has an option to display options in a checkbox / select tree."

Also, the docs have screenshots of checkboxes created using the Custom Taxonomy extension.

However, when I create a Custom Taxonomy using the Taxonomies extension, I can't see an option to create a checkbox.

How do I find this option?