Visit filebase.com
Click Get Started in the top right corner. If you have a specific link (e.g., for the MASQ promo), use that to go directly to the Get Started page.
Sign up for an account or log in if you already have one.
Navigate to Billing in the left-hand menu.
Click Upgrade on your Starter plan to go to the payment screen.
(Remember to cancel the trial before the 30 days are up if you decide not to continue with the service.)