One QBO account is for one company file. You can manage branches/divisions by utilizing the Class/Location feature. Otherwise you should open a new account.
Thanks for choosing QuickBooks Online in managing your business transactions, ajaising. I recognize how important it is to flawlessly open a new account. I'm here to help you with that.
You can open a new company file under the same QuickBooks Online account. However, each account has its own paid subscription, but you can access them with the same sign-in info. This lets you easily switch between companies while working.
Also, as mentioned by Fiat Lux - ASIA, you can use location if it's under the same EIN. Otherwise, you'll have to sign up for a new subscription.
To open an account, I'd recommend visiting the QuickBooks pricing page. Then, select the subscription. On the login page, click the Sign in link and enter the credentials used in your existing account. If you want to have two separate sets of credentials, enter a new user ID.