Go to Settings → Machine Users. If you already have a Machine User created, you can skip this step. Otherwise, click Add Machine User.
A Machine User has two fields:
Name: This is just visible to you and could indicate the usage e.g. “Autoresponder”
Public name: This is the name visible to customers (if the Machine User interacts with customers) e.g. “Mr Robot”
Click Add API Key, select the required permissions, please refer to the documentation for required permissions for each feature, copy the key, and store it safely since it won’t be visible again.