It’s time to checkout all the new stuff like Dynamics GP Essentials: GP 2015 – Understanding Vendor Approval Workflow.
Dynamics GP Essentials: GP 2015 – Understanding Vendor Approval Workflow
Payables & ReceivablesInstall, Upgrade & AdminGP 2015
Archived post from 2014. Dynamics GP and the links it points to have changed since; check current documentation before relying on version-specific steps.