It is important to track your time and expenses even if you are not being paid by the client by an hour (e.g., in contingent free agreement cases).  A proper timekeeping will help you if 1) client terminates your services before settling a case, 2) you need to file a motion for attorney fee.

You can enter your time and expenses as if the case is a normal hourly fee case.  Please don't forget to set your hourly rates for the case as indicated in the contingency fee agreement.

On case completion,  click on "Cases (Projects)" tab and scroll down to the bottom of the page on the right side panel.  You will see your billable amount and expenses.  You can then distribute the money to the client according to your contingency fee agreement.  You may also click on "Settings/Reports" -> "Staffwise Billing Report" to get billable amounts by each staff member in your firm (or your contract staff) and then distribute the proceeds accordingly.