If they are plans all you have to do is add them to the flightplan text file that ttools made use worpad or note pad to open the file then just copy the lines over.
Than use ttools to recompile and make a new traffic file
just use the aircraft.txt and flightplans.txt files as input this will make a new traffic file and will back up the orig before it makes any changes that way you can go back if there are problems. ???

there isn't a flight plans folder, there is a flightplans.txt in the Ttools folder

Add the flights to that and compile