In order to set up a service in your database, you will need to navigate to the Settings menu, over to the Items column, and then down to the Service page. There, you should be able to double click on a service that you would like to edit. Once the service pop up comes up, you will be able to navigate down to the Pricing Method drop down to select your preferred pricing method (see this article if you need help choosing a method).
If you select Custom Price, it means that you want to be able to customize the price per customer per job; you will be able to type in whatever price you like without Arborgold calculating a number for you.