RS232 to RS485

i m using RS232 to communicate with my instrument, now i would like to change the RS232 point to RS485...

i confuse with the point that i should use in RS485...

the point that i use in RS232 are TxD,RxD,RTS,CTS

but inside RS485 got TxD+,TxD-,RxD+,RxD-,RTS+,RTS-,CTS+,CTS-

which point should i use in RS485...

Thanks

485 is a differencial tranciever set.
as long as you got a 485 transmitter and reciever you aint got a problem - from the software side its almost like a 232