Premium Subscription
Either you are in the notice period before the end of your subscription, just wait for the end of the period and re-subscribe and if you are in freemium plan :
Go to Billing Overview and after go to Manage Subscription
Premium mode and pay 15$ / month per user or 120$ per year per user
choose the monthly or anualy plan and click on BUY NOW fill out the form
Each plan will be debited automatically on a monthly/annual basis depending on your subscription choice