Thanks for your advice. I followed up and It worked. When I click on RTSI cable under "NI-DAQmx Devices" folder, two NI-6034E boards successfully showed up in "Connected Devices" tab.
After right click on RTSI cable, I don't know the RTSI lines(0,1,2,3,4,5,6,7) to be checked in "RTSI Cable Reservation" tab.
I was able to add RTSI cable under the Devices tab by doing right click on devices and interfaces>>create new>> add RTSI. But When right click on new RTSI added it doesn't give me any option of adding the two boards I have i.e PCI 7833R and PCI 1422.
Although these two boards are well connected infividually and shown in DAQ but I can not add them through RTSI.