After login, click on the user symbol at the upper right corner and then on “API Key and Sub Account” to manage your master account API Keys and sub accounts.
Then in the section “Sub Account”, click on [Create]. A window will jump up and you can put an account name (a combination of 8-50 letters and numbers) and description to identify your different sub accounts and their uses. The same account name can not be used in other sub accounts.
You can create up to 20 sub accounts and once created, the sub account can not be removed or canceled.