My apologies. I really needed to clarify my problem. So I have this setup: My PC(my device) is connected to one end of an RS232 cable. The other end of the RS232 cable is connected to a R232 to USB adapter. Finally, the USB end is connected to my Raspberry Pi 3. So I enabled remote access to my Raspberry pi 3 via SSH. I followed the link: http://www.instructables.com/id/Read-and-write-from-serial-port-with-Raspberry-Pi/. So based on that link, I know that /dev/ttyUSB0 is for my Rpi 3 so I want to read whatever the PC is writing(which is at /dev/ttyAMA0). I wanted to know, to write something from the computer to the rpi3, do I just open another putty terminal so that I can see my rpi3 reading the com1 port of my pc?
You don't need to download another putty terminal to read and write. You can do both on one. if you are not getting it you can use 'Termite' terminal for this it has different text lines for read and write. If you have another problem you can ask. i also have do work on it.