Go to www.registro.br and click ACESSAR CONTA.
Add your contact/CPF/CNPJ/Domain in the USUÁRIO field and click Esqueci ou não tenho a senha. You will receive an email from email@example.com with a link to change/add your password. Click the link.
Add your new password in the SENHA and CONFIRME A SENHA fields. Remember to add a password reminder phrase in the field LEMBRETE. Click ENTRAR.
You will receive another email from firstname.lastname@example.org with a link to confirm the password. The link is only active for 24 hours.
Once you have clicked the link, you will see this screen. You will receive another email confirming your personal data and the password reminder phrase you have just added. Save this email for the future. Click aqui or ACESSAR CONTA to log in.
You are now logged in with registro.br. Here you have full control of your domains, can update your contact information etc.