Organizations are a set of Taskulu projects with similar members. When you're upgrading an organization, all the projects in that orginization are being upgraded, which means less price for more value.
If your organization has more than 10 members, you should upgrade it to Business Plan.
This could be done in two ways.
You could upgrade from the "Organization Settings".
Or you can upgrade one of the projects you have in that organization, from the "Projects Settings"
Go to "Settings", click on "Project Settings" and find "Billing" tab.
You're being forwarded to payment page, where you should fill out a form and add your personal, or company information.
In the next page, you can see your payment information. Here you can choose to pay monthly or annually. You could also select your payment method. You could choose to pay with your credit card, or if you baught credit from your profile page, you could pay with your Taskulu credit.