Hy @winanjaya. You would need to know a little bit about PowerShell.
As @rg305 mentioned DNS based verification would be the recommended method.
WAT is only the client software which communicates with the Let'sEncrypt API and handles your Certificates in the Windows Certificate Store.
It doesn't do any magic in the Challenge/Verification process. You would have to provide a script which configures the necessary DNS record. WAT will only provide you the information which DNS record is needed.
If you don't know much about PowerShell, you should really learn it! It is a great help for every Windows administrator.
Hope this helps.