For a quick & dirty procedure, setup a terminal emulator program, such as minicom, for each serial port. That will give you an interactive full-duplex interface for transferring text between ports. Several modem transfer protocols are built-in for file and binary data transfers.
For more complex data transfer, e.g. handling somekind of custom data format/protocol, you will have to write a program to access the serial port to handle the data.
Please provide more detail as to what you are trying to do. Are both serial ports to be connected to the same PC, or each port to one PC? Is there any reason why the two serial ports could not be connected to each other if that is the purpose of this "linking question"?
Since one of the "serial ports" is a USB-RS232 adapter, there's no reason to connect each serial port through a PC. Connect the two serial ports to each other (a connecter adapter may needed to be wired up), and then plug in the USB into a PC. Use a terminal emulator program to deal with the one serial port now connected to the PC.
Bluetooth <----> USB adapter <---> PC