I can't use my hp microphone keeps saying no audio input device
First of all check in the BIOS that the audio device is enabled. Then, in Device Manager, check that the sound device is properly recognized and it's driver is active - if not you will have to reinstall it. Finally , from the Realtek Control Panel check that the mic socket is correctly identified and active - take the mic out, start Realtek Control Panel, plug the mic and the corresponding icon should light up if all is ok. If it lights up but you still don't have a mic or it doesn't light up at all then the mic is dead , replace it.
If it lights up but it blink it means that it's not recognized so another window will popup, select the mic in it and it should work.