Hi Palanivelu
My name is Andre Da Costa; an Independent Consultant, Windows Insider MVP and Windows & Devices for IT MVP. I'm here to help you with your problem.
That is not correct. Just like any other computer, you must purchase a full license and install Windows 10.
http://www.microsoftstore.com/store/msusa/en_US...
Once you buy it, you can download the ISO file at the following link:
Download Windows 10 Disc Image (ISO File) - Microsoft
https://www.microsoft.com/software-download/win...
Press Command key + Space bar
Type: Boot Camp
or Open the Finder > Applications > Utilities > Boot Camp
Launch Boot Camp
Click Continue
Click Browse
Select the ISO file you just downloaded
Resize the partition - I recommend about 40 to 50 GBs or more when dual booting with Windows. See the following article for more information about deciding on space:
https://www.groovypost.com/howto/install-window...
Click Install
Wait while partitions the disk
Downloads Windows Support software
Your Mac will automatically restart and Boot into Windows 10 setup.
Remember to choose the partition during setup named BOOTCAMP.
You should be good to go.
Information in the above link is sourced from a trusted Microsoft MVP blog.