Visit sandbox website and click sign up on top right corner.
Input your basic account information.
Check your mail inbox, you will receive instructions how to activate your account. What you need to do there is to select a password and then you can sign in. After creating an account you will land on dashboard page.
Here you will see all available tokens and keys.
Copy and paste keys and tokens in your configuration or
.envfile.
I have tested this with card option and PayPal account, and it works perfectly. The purchase is performed with payer@example.com email address.
Migration From PayPal Sandbox
Moving from from v-zero integration (which requires only PayPal account) to braintree integration caused certain problems. PayPal payments were not working.
The response I was receiving from braintree by using JS v3 SDK was this:
{"error":{"message":"Merchant account not found"},"fieldErrors":[]}
The issue was similar to one described here. Also the solution was contacting support which was really responsive. In the response they said that PayPal feature wasn't enabled for some reason and they enabled it. If you face similar problem I suggest contacting support.