Building Dashboards with Microsoft Dynamics GP 2013 and Excel 2013 got some nice coverage from Inside Microsoft Dynamics GP .
Building Dashboards with Microsoft Dynamics GP 2013 and Excel 2013 – Inside Microsoft Dynamics GP – Site Home – MSDN Blogs
Reporting & BIExcel & OfficeMicrosoft & the GP EcosystemGP 2013
Archived post from 2013. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.