Configure your SSO identity store using the single sign-on guide.
From the Single Sign-On configuration page, customize the start URL for your user portal so that it's easier to remember (Note, your start URL cannot be modified once it has been customized).
Delegate IAM administration from the Management account to the Identity account following the delegated administration guide.
Accept the invitation in your email to join AWS SSO.
Sign out of the IAM management user and sign into the newly created SSO portal.
You can find detailed instructions for specific identity providers: