You can add a new company within the 'Manage Entities' page:
you will need to add the new company name and adjust the year-end if applicable. If the new company has different Netsuite or Intacct company ID's you can update them here before hitting submit by clicking the Select Different Credentials Link. Some clients will have their Trial Balances coming from different ERP systems, depending on the entity.
Once you hit submit, you will be prompted to add a mapping document to create your entity. For more information on how to prepare a mapping document, please go here.