The link that's between the business and the ATO Access Manager, is to allow the Payroll Software provider access to that business. The Access Manager does not allow you to set "who" is making the submission.
When the STP submission is made the username of the individual who makes the submission is included, thus you should have your own username with your details assigned.
If you’re sharing a login, I would suggestion creating an individual login for every person that access the payroll software.
You only need to use RAM if your Payroll Software provider is not a cloud solution.