Steps are as follows:1. First you need to turn on your Forms menu if it is not visible. Do do that, click on "View" -> "Toolbars" -> "Forms".
2. Once Form toolbar is visible, click on the "Drop-Down Form Field". This create a Drop button in the word document. Now click on the "Form Field Options" button in the Form tool bar and add the Drop-down item' by clicking on "Add".
3. Make sure you check "Drop-down enabled" option and click OK.
4. Now, click on the "Protect Form" button in the Form toolbar.
5. That's it. You should be able to use the drop down list now.