Firstly, you need to make sure that you have either PoE injectors or a PoE switch to connect and power up your IP cameras. We've got a range of those here, if you need them. Make sure that whichever PoE supply you choose has enough power budget (ie. wattage) for each camera's requirements, as well as a spare port to plug back into the rest of your network.
Your IP cameras will be communicating via the PoE injectors or switches, through the modem/router, and via the LAN port on the Doss Hybrid DVR. Have a look at the diagram below for an example.
OK, beyond the physical and electrical connections, the other part that needs to be configured is in the software for the hybrid DVR.
Log into the DVR (if you aren't already), and go into the "Settings" menu, then into the "Device" -> "Device Info" tab.
At the bottom of the "Device Info" page, there is a drop-down menu called "Stream Type".
By default, our hybrid DVRs are set to a stream type that supports only coaxial cameras. If you check the drop-down list, you'll find stream types that have "IP" in them somewhere, and those are the mixed coaxial+IP camera types. The rest of the information shows you how many cameras, and at what resolutions. From the image above, the second option would give you eight coaxial cameras at up to 2MP/1080p per camera, plus eight IP 2MP/1080p cameras. This system would not support 3MP/4MP/5MP/4K cameras.
After choosing the appropriate stream type for your requirements, click the "Save" button in the corner. The DVR may ask to reboot to apply the settings, and then you should have the option to search & add IP cameras to the system, generally from under the "Channel" settings menu.
Please note: The way the cameras are allocated on the "Preview" screen is that the first eight windows (for example) will display the coaxial cameras even if you only have two connected, and the next eight windows will display the IP cameras even if you only have 3 connected. Depending on the age or generation of the DVR, you may be able to click, drag and swap these cameras around to match your preferences, or they may be fixed, requiring you to see a lot of black windows for disconnected cameras.