very new to Constant contact need assistance

Hello, I have now been given access to Constant contact as an account manager. I am the new owner of the company and the employee who set up the account is no longer working for the company and i require to be the Owner of this. how do i change this over. I also need to do something with the DNS. I have to update payment to our business banking account, add more users. how is this done please and thanks!