When you create your new Overflow account, an organization named "<firstname> Organization" is created for you.
To create a second organization in Overflow, go to Overflow Cloud and sign in to your account. You'll find the Organization menu at the top left on the Dashboard.
Click "+ New Organization". You'll be taken through the steps of purchasing a new subscription. Depending on your team's size and needs, you can choose the number of seats and billing cycle (monthly or yearly).