To join the my.siyli platform as a Certified Teacher, you have to first be invited by SIYLI staff.
You should receive an invite at your registered email address, with a link in it - this link will allow you to set up a password for accessing the site.
If it's been a while since you go the invite, your link may have expired. In that case, navigate to the 'forgot password page', and type in your email address (the same one where you got the original invite), and you should receive a new link in your email shortly.
In case you haven't gotten that email from us, contact firstname.lastname@example.org and we can help you out.