This method assumes that a volumetric flask with capacity of 1.00 L is available, along with apparatus for measuring an arbitrarily chosen volume between 0 and 1 L to three significant digits of precision:
First calculate how many moles of HCl are needed for the volumetric flask. Since "M" means moles per liter, this value is 0.646 moles.
The calculate how large a volume of the 2.00 M solution is required to contain 0.646 moles of HCl. This value is (0.646 moles)/(2.00 moles/liter) or 0.323 liters.
Then transfer this amount of the 2.00 M solution into the volumetric flask and dilute to the capacity mark with distilled or otherwise purified water.
You can prepare 1.00 L of 0.646M HCl solution by diluting 0.646 L of 2.00M HCl with water to a total volume of 1.00 L. To do this, measure 0.646 L of 2.00M HCl using a graduated cylinder and then add water to bring the total volume to 1.00 L. Mix well to ensure the solution is homogeneous.