Authentication is done by Key Key, a sequence consisting of up to 128 characters.
In each request whether made via POST, GET or JSON the parameter key must be configured with your key.
If you already have an account, go to https://painel.smsdev.com.br/configuracao/conta/perfil
Subaccounts have their own Key Key, just login via Subaccount and access the same url above.
To change it is necessary to request via email to email@example.com.
Create a free account at https://painel.smsdev.com.br/criar-conta.