Interface an RC System 4 Channel Digital TX with FMS on Wind

[eurosystem0]

Anybody help. I have downloaded FMS 8.5
The TX has a serial lead.
My dell PC does not have Serial port.
I have bought cable that converts Serial to USB. I also have a small software disc with it that has loaded succesfully on XP . In siftwar load help it only refers to 64 bit.
My PC recognises TX hardware .
I can run FMS. I can operate FMS using keyboard.
I have gone into FMS Controls, selected, Joystick, PIC,resources and selected Com port recognised by PC for hardware. selected mapping.

Dont know what to do next. when I move TX controls nothing happens to calibrate. don t know what boxes to tick etc

Oh. This is the first time I have had a RC model its a helicopter 4 Channel.

Ive been at it for hours trying to get the bl***y thing to work.

Can anybody help this total novice.