Microsoft Dynamics GP 2018 was released in December 2017. Dynamics GP 2018 R2 was released in October 2018. Here is a quick list of all the resources you need:
Product Release Downloads for Microsoft Dynamics GP 2018
Dynamics GP 2018 System Requirements
Dynamics GP 2018 System Requirements Web Components
What’s New in Dynamics GP 2018
What’s New in Dynamics GP 2018 R2
Features Since Microsoft Dynamics GP 2013