OK first you need to set your IP address of your network card to be in the same subnet as your PLC IP address, but be careful not duplicate and existing addresses.
So if your IP address on your PLC is 10.64.8.91 then your PC will need to have an IP address in the range 10.64.8.xxx range.
Open up control panel and go to your network settings and change the IP address as in the picture.
Your probably missing the EDS file for that plc. If you could provide more information what type plc, what software you are using (logix5, 500,5000 etc.) what version your software is and what version linx.