Joining the insider program while I have the disc for the game...

I just tried to join the sea of thieves insider program. I tick the box that says I accept the terms and conditions and then I press submit. But then I am greeted with a message that says "sorry, we can't seem to find your sea of thieves pirate". Now, I can clearly tell why this is. It's because my xbox account doesn't own the game because I play it using the disc for the game, but I would really like to know if there's a way to join the insider program with the disc. Can anyone help me out?