To set charges for your assignment types, you need the "Visit Types" tab under the "Settings" menu:
Charges are inputted on rate cards, which are located under the pound symbol to the right hand side of any assignment type. Choose which assignment type you wish to set the charges for and click the pound symbol. You will then be presented with the rates and charges. There are two different rates for each card - Variable and Fixed.
Variable rates allow you to have different rates for different times of the day,different lengths of assignment and bank holidays and weekends:
Fixed rates, as the name suggests, are a fixed cost for that particular assignment type:
After selecting whether the rates are fixed or variable, simply enter the charges, ensuring you click save afterwards.