With that old controllers nothing is easy going.
They don't have an ethernet card as standard, so You will need that option (hardware).
Then You can connect a PC to the controller via ethernet cable.
Watching I/O's is, as far as I know not possible (May be with additional software from ABB, which will be very expensive or not supported any longer).
The only thing that I know is: You can transfer files from Controller to PC and vice versa via NFC- or FTP- protocol. And that's only possilble if the option NFS-Client or FTP-Client is installed on the controller.
For the NFS thing You will need special software on the PC, which often is tricky to configure. The FTP thing is a bit easier to configure.