there are a number of different approaches to get video output (from what I'm guessing is a cheap IP security camera?) to a streaming service
RTSP is a common protocol
Upper end cameras (ex professional PTZ units) use other protocols, like NDI
Though a terrible quality approach, you could have OBS scrape/capture the web interface you are watching the camera on [not a recommended approach]
So what should you do? depends on capabilities of your specific camera [which I'm not familiar with]. Assuming it supports RTSP, then looking up in this forum VLC, RTSP and IP security cameras should point you in the right direction... beware passwords which may work from a browser but won't work when using RTSP (ex using certain restricted characters like ?... it depends on the camera firmware and the s/w you use to connect to camera and present video stream to OBS with)