When a new user is invited, they receive an email with instructions on how to accept the invitation. It is most convenient to accept the invitation, without creating a new account from scratch.
You can copy the link and share that directly once the invitation has been created, if the email gets into the spam filters or something.
However, if a new account is created, once the user logs in, the invited organization will be found in the Linked Account. It is essential to create an account using the exact same email address as the one specified in the invitation.