Braintreee

1. Setup a Braintree Sandbox account

Go here to create your Braintree Sandbox account

2. Setup the merchant account

On the top menu go to:
Account
and select
Merchant Account Info from the dropdown

In the page click on the
New Sandbox Merchant Account, the window below opens:In the form set a name in the field 
Merchant Account ID

Check the - Make this my default merchant account.

Don´t forget to choose the correct currency

3. Get the requiered data

Next select Settings in the top menu then click on API Keys
In the API Keys table
Click on view
There you will find the Merchant ID, Public Key and the Private Key

Copy one of them and paste them in your solution

4. Inserting the correct data in Experience.live solution

From the settings menu select Company settings

Under the Braintree sandbox credentials enter the Merchant ID, Public Key and the Private Key.

5. To test you can use a test card

Click here for test creditcard data

To get the real account up and running follow the steps above but use this link to setup the account, do remember to set this up in an early stage of your testing beacuse there is a bit of paperwork to get it flying.

Good luck