The DataVideo KMU-100 produces 4 1080p feeds (or 1 4k and 3 1080p feeds) from each input and has 2 different inputs. It is possible to link the input on Signal Input A with the input to Signal Input B, but in this case, the connections for Signal Input B will not be used and the signal from Signal Input A will be sent to both splitters to make 8 1080p feeds.
If you want to have two feeds, you need to make sure each of the Signal Input sections is properly configured in DV Link. You will want to make sure each camera is plugged in appropriately on the back. There are 3 possible ways to plug your camera in to each bank. Only one camera should be plugged in per input block (there's a square around each set of 1 HDMI and 4 BNC connections.)
If your camera is HDMI based, you will want to use the HDMI connection. Note that if your camera is too far away, the HDMI signal may have trouble making it to the splitter and it may be necessary to get an HDMI to SDI converter for longer runs.
For single link SDI (3G, 6G, 12G) I would connect to the 12G BNC connector. It should be backwards compatible with both 3G and 6G and should give you the least possible headaches. The manual is a little unclear on this, so I'm having to make an assumption, but given that the other's are all 3G, they appear to just be there for dual and quad link signals.
For dual and quad link signals (where two or four 3G cables are used from a single input source), use the necessary number of connectors regardless of if they are 12G or 3G. The manual isn't clear on which ones should be used, so presumably the unit can figure it out on it's own. If you have problems I might try using different connectors for the dual link.
Once you have everything setup and the type of line selected in DV Link, the feeds should be detected provided that your cameras are outputting on a compatible video format. It appears that the unit has it's own frame synchronization so it does not appear that video settings have to match between inputs, but if you experience problems, it couldn't hurt to verify this as well.