1. Log in as the admin of your company account.
2. Visit your Settings.
3. Click Choose A Plan (if you're already on a paid account, this will say Change My Plan) from the settings menu.
4. Select the plan that fits your needs.
5. Complete the contact and billing information form (you won't need to do this if you already have a paid account) and click Upgrade account.
Congrats! Your account will be upgraded immediately and you'll receive a confirmation email.