How to take such photos?

I have a NIKON D5200 and I want to know how to click such amazing photos

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Spend several years learning how to properly control lighting, exposure, and depth of field. Photography is like everything else in life, it requires time, experience, and education to become good.

Sorry but I'm not quite sure why you think they are "amazing"
They are good portraits with lighting used to good effect. But nothing that any reasonably skilled camera user couldn't achieve.
The first one has some fill in flash to the front.
The second is lit from the side (left)

Seems you have posted a couple of fairly average portraits rather than "amazing photos".

If it is in fact the correct shots you posted then you take them by framing, focusing and exposing a photo properly.

I agree that the portraits are nothing special and simple to achieve especially with a good entry level DSLR like the D5200 you are using. There are loads of tutorials on the internet showing you the best way to light and compose your photos, once you begin to practice you'll soon realise its not that difficult to achieve the results you are looking for.

And I will simply add this

Very average pics. To relicate you just need two pieces fo equipment:
either a lens with a very low aperture. In your case a 50mm f1.4G would be perfect and if too procey the cheaper 50mm f1.8G would be ok.
off camera flash: An SB 600 would be perfect for your usage unless you have very deep pockets and want to get the SB910 (my flash of choice) but really not necessary for non-professional use.

Good additional items: A tripod for your camera and another for your off camera flash. Camera tripod, try to get something which is solid and not made from aluminium.

More importantly, learn to use your camera! Knowing how to set your white balance, exposure and shutter speed depending on what you want to get is an essential skill regardless of the type of photography you are involved in. Photos like these will become second nature very quickly and once the absics are mastered you can actualyl start looking for the amazing pictures