Open the ArcMap document and activate the WebOffice author toolbar by clicking the button WebOffice author for ArcGIS 10.4.

WebOffice author toolbar in ArcMap

WebOffice author - default view
In case no ArcGIS Server publisher user (find details in chapter Configure ArcGIS Server Publisher Account) was configured yet, a notification message will appear in ArcMap after clicking the button WebOffice author for ArcGIS 10.4.

Notification: Configure an ArcGIS for Server publisher user
After confirming the notification message the list of ArcGIS for Server publishers will be displayed. Now it is possible to configure an ArcGIS for Server publisher user.

Configuration - ArcGIS for Server publisher user