3. Select a Custom Protocol , such as custom protocol 1, then change the protocol name as you need, like ANNKE RTSP. Type in the stream path of main stream and sub stream of your IP camera. Click OK to save the settings.
Note: Different brands of IP camera have different RTSP formats. Please find the RTSP format of the IP camera by yourself.
As for ANNKE cameras, the stream paths are as below.
Main stream : ch1/main/av_stream ; Sub stream : ch1/sub/av_stream.

4. Then Go to Menu-Configuration-Camera-Camera-IP channel, select an unused IP channel and click edit.

5. Change adding method from plug-and play to manual, type in the IP Address of your IP camera need to add, and choose the RTSP protocol which has been created before from protocol list, then fill in the User Name and Password of your IP camera, click OK to save the settings.

6. Finally, the IP camera will online with your custom RTSP protocol successfully.

You can also perform the same operation through the NVR's web setting interface.
Here is a link for your reference about how to visit the NVR via the web: Annke Vision - How to Access DVR/NVR System on The Web Browser from PC(in the Same Local Network)?
If you have any other questions, please contact ANNKE technical support at support@annke.com by email.