When you save CRTX chart templates, PowerPoint saves them into a default folder location. As long as you are using these templates only on the computer where they are saved, there is no need to worry about this default location. However, if you need to share these CRTX chart templates with other users — or, if you received a CRTX chart template from someone else, then you need to make sure that these CRTX files are saved in the designated folder where PowerPoint expects them to be placed.
Learn about the default location to save chart templates in PowerPoint 2011 for Mac

