The FAA will transition to mandatory use of the international flight plan format for all IFR and VFR domestic and international civil flights on August 27, 2019. The change is part of an effort to modernize and streamline flight planning and supports the FAA’s NextGen initiatives. Several improvements to the international form make it easier and more intuitive for pilots to use and will increase safety, including an increase in the size of the departure and destination fields to allow a greater variety of entry types, including Special Flight Rules Area (SFRA) flight plans.
Many resources and videos are available to help you setup your preferred flight planning tools. See the links below:
Help with an ICAO Flight Plan (FAA document)
The ICAO Flight Plan (AOPA video)