Download the package and adb.zip to some folder, say c:\e1m1
Unpack adb.zip into same folder.
Open command line and go to folder with 
cd c:\e1m1

Now, enter recovery mode on Nokia 2 :


Shut down your Nokia smartphone.
Connect a USB cable (charger or PC) and wait for the device to start charging.
Press and hold Volume Up & Power key(s) together. 
Release the power button upon vibration, but keep the volume key pressed.
Your Nokia phone should boot into recovery mode. 

After  entering  the recovery, you will generally see the "No command" screen with a
dead  Android  bot  and  a warning sign. There is nothing wrong if you see it. To
proceed  further:  Press  and  hold  Power key and quickly press and release the
Volume Up key. Release the power key when you see the recovery options.


Now, select "Apply update from ADB"
New Device will appear, but driver will not be found,even in you installed 
drivers from HMD Nokia tool drivers folder.

Manually install device driver for this device - select 
update driver
browse my computer for driver software
let me pick from a list of device drivers on my computer
select manufacturer "mobile", model "ADB interface"


Now, go to command prompt and type
adb.exe sideload E1M-064Q-0-00WW-B01-064J-0-00WW-B01-update.zip

Wait until completion, you will see error messages on phone screen, this is ok.

now phone bootloader downgraded, flash firmware with HMD Nokia Tool and do your job.