Select 'CONFIGURE CABIN LAYOUT' from the side menu
Select the Aircraft type you wish to create the layout for. Note : a layout for a 737-300 will not fit a 737-400 it has to be for the specific type.
Assign seats to first, business and economy classes.
The next screen will allow you to select your IFE for the different classes. You can have different ones for each class or the same or none. You need to have created the IFE before you configure the cabin.
hope this helps :-)
PS once you've set up a configuration you can select that configuration for any new planes you buy or lease. Pre-owened or Used Aircraft will have to be configured after you've bought them but the new ones will come ready fitted. You can select for batch conversion of the same type ie A320-200 or do each aircraft individually.