How do we specify which account (s_account) is used for tracking?

### Expected Behaviour
I'm new to the data layer concept. I'm not sure how to target an Adobe account and tracking server using this API. Where do I provide the s_account so I can target our Dev or Staging or Prod accounts? Is that part of the data layer JSON object or is it a global variable I need to set?

### Actual Behaviour

### Reproduce Scenario (including but not limited to)

#### Steps to Reproduce

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#### Sample Code that illustrates the problem

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