Johnston has his Level 3 coaching certificate and is studying towards his A-Licence, the highest qualification a coach can obtain in Oceania.
"We have to make sure we can provide as many opportunities for our talented and developing players - from the top of the Brynderwyns to Cape Reinga - to excel as possible because everything is there, we just need to put it together," Johnston said.
The move from the NFF means Johnston will be focused on Northland's representative football teams (with the exception of the 12th-grade Weir Rose Bowl teams) alongside continuing with his role as men's first team coach.
'It's a big challenge. I want to thank Dave Alabaster and NFF for providing me with the opportunity to develop my skills as a coach," he said.
"I can't wait to do my bit in taking the club forward and working with the best players and coaches in Northland.
"Training doesn't stop at the end of the season although the trainings are a little less intense they are still valuable and a chance to improve yourself. Soon it will be time for us to start getting ready for 2018 and we will be off again."