The compiler is looking for something called look into the type OnFootAction, If you've followed the tutorial accurately, the correct syntax is not onFoot.look.ReadValue; it should be onFoot.Look.ReadValue. Pay attention to the capital 'L' in "Look." This tutorial is likely by Natty Creations.
void LateUpdate()
{
look.ProcessLook(OnFoot.Look.ReadValue<Vector2>());
}