Maybe…a new Amazon seller

Hi! i want to create my notebook with Canva and selling it on Amazon. I have checked many videos and read something about it but I am still confused. I don’t have a business… Can I still create my Amazon business account? If i earn more then £1000 I have to pay tax. But what if this happens in future. Whene is the right time to open a self employed account with HRMC? Thank you