1. To enter an hourly billing item, enter the time (either hours/minutes or tenth hours format) in the provided boxes. System will automatically calculate the amount based on your hourly rates. (by the way, you can set different hourly rates for different cases. Click on the "Staff Access/Rates" tab, select a user, an "Edit" link will appear next to the hourly fee amount. If you don't set a different hourly rate for a user, the user's global hourly rates will be used automatically.
2. To enter a flat fee item, simply enter the amount in "Total Cost" box and don't enter anything in the "time" boxes. (this item will displayed as a "Flat" fee item on the invoice. Do not check the "expense" checkbox.
3. To enter an expense, click on the expense checkbox (and leave Billable checked). Enter number of units in the box shown and then enter the total cost in the "Total Cost" box. For example, if you want to enter charges for 10 copies @ .20c/copy, enter "10" in the "Units" box and then enter "2" in the total cost box. This item will be shown as an expense in the invoice.