How do I use my full Windows 10 account in the regular desktop app?

I bought the full version of Minecraft in the Windows 10 app for my kids a while back... and now my daughter wants to try coding Minecraft. I downloaded and installed the desktop version of Minecraft, but don't have a Mojang account.. only a Microsoft account. Is there any way at all to use that same account on the desktop app? I don't want to pay again.

I'm afraid that if you want Minecraft Java edition, that you'll be paying full price for it.

As of 19 October 2018, Minecraft Bedrock edition (windows 10 app) and Minecraft Java edition ("desktop version") must be purchased separately. Details can be found here:

https://help.mojang.com/customer/en/portal/articles/2064007-minecraft-for-windows-10

Prior to October 19, if you bought Java edition, you could get a redemption code for Bedrock edition. Unfortunately, it doesn't work the other way around.