How to reference fields w/select box defined?

I am new to Feeds and trying to implement to import a certain content type on a regular basis. The definition and mapping was going well but I in my list of target fields I do not see at least one which is defined as a select list in the content type definitions. Unless I am missing something entirely I have not been able to find any documentation or references to such fields.

Here is the top portion of the content_type defintion for this field:

Edit basic information
Field name: ______
The machine-readable name of the field. This name cannot be changed.
Label: * ______
A human-readable name to be used as the label for this field in the Course content type.
Field type: ___
The type of data you would like to store in the database with this field. This option cannot be changed.
Widget type: Select List
The type of form element you would like to present to the user when creating this field in the Course content type.

So my question is: How can one create/update a field that uses a select list (the actual database stores the user_id of the referenced user(s).

Thanks