How do I place mountain ranges?

[Rochnan]

Hello Laughy,
my mantra is: everything happens for a reason.
That's a good thing, because having a reason to put mountains somewhere is what makes them look natural, and as an added bonus can open up story or lore.

So, this is what I did:

From the top:
The grey area is mostly shaped by activity below the world's surface: magma pushing up. It's strongest to the north creating my beautifully jagged volcanos (should I have drawn lava for clarity?)
Below those, the magma didn't really break through the surface but did manage to push it up. This creates dome mountains.
The blue is where I had an ice age happen. The resulting glaciers didn't really create mountains, but instead left a very hilly landscape. Think northern England.
The magenta fault line represents where the (originally two separate) landmasses/tectonic plates collided millions of years ago. This created nice peaky fold mountains from one side to the other side of the continent.

The rest is relatively flat. But that doesn't mean there can't be mountains too! Maybe erosion created some nice plateaus. Who knows?

If you want to know more about mountain types (which will hopefully inspire you), I suggest visiting this page.