Visibility of Fixed Fees (FF) in the Ready to Bill section is dictated by the data associated with the FF. If you didn't specify a date, it would have been assigned when the FF was created.
For Items you will be billing in the future:
To change this, head to the Matters Page. Select the matter where the FF date needs to be adjusted. Tab to Access and Billing. Double click on the fixed fee item. An editing screen will appear. From there you can set the date to a time in the future.
For items, you don't intend to invoice:
Head to Ready to Bill. Select the FF matter you want to move from Ready to Bill and allow LeanLaw to enter the first stage of the invoicing process. You will see a "clear" function next to the FF line item (see image 4 below). This will mark the time entries in this group (1 total) as "processed" so that they won't show up anymore in Ready to Bill. It will NOT delete the time entries- they will still count for reporting purposes