Please select the relevant link from above for your recorder, 

Once downloaded, please extract the file and copy the folder "hdvrupgrade" over to a flash drive,

Insert this into one of the available USB ports on the NVR 

Open the setup screen, go to System > Maintenance and select Upgrade 

No select "Choose FIle" and select the .SW file from the USB Drive and select OK. 

If you have created a password for the recorder , you will need to enter this to confirm 

The install will now proceed , once the unit has rebooted the installation will begin.