How to create a desktop software with a website API and create license?

I am looking to build a software for desktop that uses a website API to login to the software and create a license for each API of the site.

So, while opening the software it should ask for a license key (license key will be provided by me with loaded API of user's account )After the user logins into the software with the license key their account will be visible in the software.

I don't want to openly share the api inside the software rather I need them stored inside a server so they cant create a 3rd party app. Looking for some help and not a native English Speaker!

Thank You!