How do I pay annually instead of monthly?

To change your billing detail, on the top right hover over your name and from the dropdown menu select Plans & Billing.
In this location, you will be able to modify the type of paid account you have, update credit card information, and even pay annually.

To switch the billing between monthly and annual toggle the switch above the plan table.
Select a plan, enter your credit card details and confirm that by clicking Submit.

Your billing cycle and renewal date will change immediately.

How your plan is prorated for an upgrade or downgrade?