Click on Billing, fill all the mandatory fields and click on "Update card Details".
These Updated info will be saved in Subscription.
To verify whether the updated billing is saved or not go to CompanyDetailsSubscription
After clicking on subscription you will get a slide in which it contains "UPGRADE" button.
Click on upgrade button it will be redirected to Omsplanselect page.
In that page you can see plans like Basic, Enterprise and professional choose any one them by clicking on "Choose Plan" button.
After clicking on choose plan button it will redirect you to OMS>>Checkout page
In this Checkout page you can see the saved billing information and order summary.
From the Order summary choose the multiple choice boxes depending on your requirement and fill the text box of order notes if needed and click on "place order" button.