I've been checking on how you can access your candidate information/registrations/results if you are taking exams, now that the RHS has a new 'Portal'.
I've had a reply from Carol Johns (who is very helpful, along with her colleagues, if you have any problems - email email@example.com).
Regarding students creating their account, they should receive an email invitation inviting them to create their account, if they do not receive this they need to go to https://candidate.rhs.org.uk/Login.aspx and then follow the instructions on the page.
She also says that:
I'll post this information in both Chat areas as well.