When you click the ‘Exclude’ tab, options for exclude will appear.

Exclude (Posts)

The IDs of any posts you want to exclude, separated by commas.

Exclude (Categories)

Select checkboxes of any categories you want to exclude.

Exclude (Tags)

Select checkboxes of any tags you want to exclude.

Exclude (Custom taxonomies)

Select checkboxes of any custom taxonomies you want to exclude.

Displays checkboxes of them when there is any custom taxonomies.