Pour 100 mL of the 10N HCl into 400mL water.
Dilutions are ratios of the Normalities.
This means that 100mL of 10N HCl contains as much HCl as 500mL 2.0N HCl.
To make 500mL of 2.0N HCl solution we need to dilute the stronger acid with water.
NEVER pour acid into water!!! You need to pour the concentrated acid into the diluent water.
If this were for an actual calibrated volumetric amount, we would pour the acid into slightly less total water - say 300mL – in a calibrated 500mL volumetric flask.
After the solution had cooled down to constant temperature (actually, it is usually 25’C for accurate flask measurements) we would finish the dilution by adding water to the calibration mark.