So what you have is a gaming headset.
Ie: Headphones with a mic on the headset on a arm where you can move it up or down to position the mic next to your mouth.
It is not selected as a Mic or a set of headphones.
Nor will any selection in the realtek bit of software provide it.
Instead first of all on the windows desktop right click on the speaker icon next to the time.
Select playback devices.
You will see if your headphones are connected a listing in playback devices.
Right click on it and select set as default communications device.
If you look up to the top of the window you will see the tab recording, click on it.
You will see a listing either of the headset or the mic of the headset.
Once again right click and set, or select as default communications device.
If you wish to use it for hearing in game sounds and chat, and to be able to talk to others, the headset must have two 2.5mm jacks one for the sound playback and one for mic input.
If you are trying to use headphones, with a built in mic meant to be used with a mobile phone where it has one jack with three rings on the jack end it will not work with your PC when connected via a one jack input.