File properties in Word (or any Microsoft Product) tell the document information such as the number of pages, the number of words, the author and much other information. The property is important especially if you want to claim you are the author of the document.
Step 1: Click the "File" tab from the ribbon;
Step 2: On the right side, you will see the list of the property;
Step 3: You cannot change all the information, but you can change some of them. For example, you can change as the title, tags, and comments and the author.
For most parts, you need to click then type to change the properties.
To change the author, you will need to right-click on the author name, and select "Edit" from the drop-down list;
Step 4: Type the new name in the "Edit person" window, and click "OK" to finish.