That tool is part of the AutoCAD content, not the AutoCAD Architecture content. When the program was installed, If you chose to create a profile to run AutoCAD Architecture "as AutoCAD", then you should have an AutoCAD profile, and, possibly a desktop shortcut labeled something like AutoCAD Architecture 2015 - English as AutoCAD that will start the program using that profile. The exact name may vary, depending upon the content you installed and where you are located.
If you do not have such a profile, creating a new profile on the Profiles tab of the Options dialog, and then selecting it and selecting the Reset button will create an "as AutoCAD" profile.
With an "as AutoCAD" profile current, you should get the vanilla AutoCAD sample palettes. You may have to type TOOLPALETTES at the command line and then press the ENTER key to turn on the display of the toolpalettes, if they are not already open. The Annotate palette has sample content for both Imperial and Metric units, and each subset includes a Graphic Scale tool that inserts a Dynamic Block representing a graphic scale. The imperial version does not appear to have architectural scales built into it, just 1" = some distance, but perhaps you are using metric units or need to show imperial "engineering" scales.
The AutoCAD Architecture content includes a Bar Scale tool in the Stock Tool Catalog, in the Drafting Tools category.

David Koch
AutoCAD Architecture and Revit User
Blog | LinkedIn
