I have tried through the NVR and cannot find settings for flash and sirens are they only available by going directly through web interface??
Yes, the control for siren is only on the camera web interface. This is quite annoying as the siren by default will sound when IVS rule triggers.
On my poe NVR, I do the following.
On camera registration page, you should see "e" next to each camera listed, click that, should open another tab, enter same password as nvr.
If you can't see video, connect computer to spare poe port on nvr, log into nvr as normal, click "e" on camera registration page. Log into camera, when "download plugin " appears where video should be, click save&run. Next time you can login as normal via wifi, and video should still work.