How to convert the video to 60 FPS?

I want to know how to convert an video to 60 fps like the ones in youtube

There is no point in artificially building up a film in 60 fps if it has fewer fps in the original source.
Otherwise export under ‘extended’ at 60Fps, but you will see no difference that the exported film is not ‘smoother’.

Can u tell me how to make it smoother ?

You already double-posted:

oh sorry about that . Did u watch the videos ?

Yep!

Why do the videos have an impact , i mean why it looks smoother ??