Purchasing and licensing: bought from Apple

You have said that you have bought the Universalis app from the App Store.

If you want Universalis on Mac or Windows

The Universalis programs on the Mac and Windows are free to download and they work for a trial period without requiring payment. After that, they need a registration code.

Since you have already bought the Universalis app from Apple, you have already paid half the price of a Universalis registration code. So you can now buy a registration code by paying the second half of the price. The code you buy will work on Amazon devices, Android devices, Mac, Windows, and e-books.

You will find the purchase instructions here.