There are a number of filters available to you on the Contracts List (Accounting > Contracts) that can help you customize the page view:
These filters correspond with the columns on the table further down on the same page.
The Client filter will open an open text field where you can search for the Client's first name, last name, or their name exactly as it appears in the Client column. If their name is listed Last, First but you search First Last, your search will not yield results.
Use the Service filter to search for any of the text that appears in the Service column. Remember this column's source is actually the Contract Name field on the Contract overlay:
The Billing Day filter will remind you to enter a number between 1 and 31. The Amount filter is another open text field. You only need to enter digits in this field, you don't need to enter a dollar sign. The Start Date and End Date filters will each open a calendar date range. You can either type in a date or select from the calendar dropdown.