That is one confusing article!
You will need to use the
Developer Tab, as was mentioned in the Microsoft article.
I am assuming that all users of your form will be using Word 2010 or later.
Insert Content Controls where you want your user to input data.
If you use
plain text content controls, the tab key will move to the next control.
If you need something input by your user to be repeated in multiple places, see
Mapped Content Controls and Document Properties and
Repeating Data (Populating Multiple Like Fields).
When you are done creating your form, restrict editing to no changes with exceptions. (See below.) Make sure that developer mode is turned off.
Here's another confusing article that may be of help:
Making Forms with Microsoft Word