Thanks for getting back to us Louise and apologies for the delay, I'm not sure how the previous reply was missed!
On the advanced payroll you can set the fixed hours by going to Payroll from the left menu > Select the employee listed > Pay run defaults > Under 'Standard Work Week' > 'Based on a standard' enter the total no. of hours per week and tick 'Pay these earnings by default in a pay run'.
You can also instead of checking the option above go to 'Pay rates' and enter the rate and units (total hours) per month against the specific pay category and tick 'show in pay run' - this option is useful if the employee's hours are split under different pay categories. :)
Get back to us below if you have any Q's!