If you are new to Windows 10, you may be wondering where to find the OS build information. Well, you can firstly head over to Settings -> System -> About and can see the information as below:
Or you can use PowerShell and run a simple command to give you the same info, here is the command:
Type in the command and press enter and you will get a screen popup as per below:
There are many other commands you can run that will give you other info but if you want the basics, the above should suffice.
Hope it helps.