Prior to relocating, the primary residential parent must provide the other parent with notice of the intended move. The other parent can then object to the move.
If the other parent fails to object, the move will be allowed. If the other parent does object, then the court will schedule a trial date and ultimately decide on whether the children are allowed to relocate with the primary residential parent.
There are many factors the court will consider in deciding whether the relocation will be allowed, including the impact the relocation will have on the existing parenting plan, the logistics of maintaining contact with the non-relocating parent, etc.