Which NVR is it?
Most of them can pass the signal to BI.
Simply go to "add camera" and type in the IP address of the NVR (not the camera) and put in username and password and hit find/inspect and let BI do its thing.
Then midway down is a section to add a camera number, so select camera #1 and save/ok and it should pop up.
If it does, then add another camera, copy that camera, and then change #1 to #2 and repeat.