Within Teamwork Spaces, you can create a paid subscription for your site at any time.
Click your profile icon in the top right of your site and select Settings from the dropdown menu.
In the settings area, select the Subscription tab in the left sidebar.
Click the green Choose a subscription plan button to proceed with the checkout process and choose your team size.
In the checkout area, you can use the Team Members text field, or the team size bar below it, to set the number of users for your subscription.
The pricing calculator will automatically update to reflect the team size you have entered. You can also opt for monthly or annual billing here.
Click Select to proceed to the payment details.
To cancel your account, select the red Cancel account option within the Cancel Account area.
For more information, see: Using the Teamwork Spaces Pricing Calculator