Sorry.. the docs display a fairly (unfairly) dated version of WD .. sorry.
Use WD, Control Panel, Internet File Creation & Uploads, Setup Page#2
press 'Set' next to File#29 to open the dialog
Enter 'testtags.txt' for Local Filename
Enter 'testtags.php' for Remote Filename
Click on Show Create Times. Click on 'Update every 5 minutes'
Click on Show Upload Times. Click on 'Update every 5 minutes'
Turn 'Use These Settings' switch to ON, and press Save and Close.
You should see two green balls on the File#29 line in the Setup Page#2 dialog.. that will indicate the create/upload are both set to on.