In this section the used forcefields can be chosen. To add a forcefield select it from the drop down menu and then click 'Add forcefield to list'. In the appearing popups you have to define various parameters. Your selection of forcefields will be shown in the box below.
'Delete' removes a single forcefield from the list.
'Clear' removes all forcefields from the list. You will have to select what scale and what depth the forcefield should have. For more information about each energy term click here.