Create Vocabulary in nuxeo platform for dropdown widget.

* Add your options in the vocabulary section & choose your vocabulary type according to your business needs

* Select your document type

* Go to schema section

* Add a new field

* Select your data type as directory

* Select your vocabulary 

* Save your document type

* Configure your layouts like create, edit and meta with new field changes

* Hot reload your configuration

* Now you can see the new changes in the nuxeo platform.

See the complete walk through session from the youtube.