The first step is to create a new dLocal merchant account here: https://merchant.dlocal.com/sign_up
After submitting information, you will receive a confirmation link from email@example.com in your email address. Verify the link, and you are all set to access the panel.
Access the merchant panel through https://merchant.dlocal.com/login using the email and password you set when signing up. You are now ready to operate in the Sandbox environment.