I have a none flat terrain as a triangle mesh( vertex & index buffer) . how to define physics to it using PhysX

I am trying to find out how they did it in their Sample bridge

P.S I am not using Game engines.

I am fiddling with the code but I have no clue about what am I suppose to do

I have mesh created with DirectX so i copied the mesh Vertex and index buffer for physics

I made PxTriangleMeshDesc

physx::PxTriangleMeshDesc meshDesc;
meshDesc.points.count = nVerts;
meshDesc.points.stride = sizeof(DirectX::XMFLOAT3);//I decided not to convert it for now and see how it goes
meshDesc.points.data = verts.data();  //this is unique vertices

meshDesc.triangles.count = nIndices;// each 3 indices are triangle
meshDesc.triangles.data = indexBuffer.data();
meshDesc.triangles.stride = sizeof(uint32_t);

then I cooked it or whatever using cookTriangleMesh
then I created triangle mesh PxTriangleMesh, then PxTriangleMeshGeometry then i made PxRigidStatic then i created exclusive shape then added the rigid actor to the scene and saved the actor

now I am lost, I have no idea the following code does, I can guess that it creates a mesh for render, but I already have rendered mesh so should I ignore it

   PxShape* shape;
   actor->getShapes(&shape, 1);
   RenderMeshActor* meshActor = createRenderMeshFromRawMesh(data, shape);
   link(meshActor, shape, actor);
   meshActor->setEnableCameraCull(true);

but then what is linking

void PhysXSample::link(RenderBaseActor* renderActor, PxShape* shape, PxRigidActor* actor)
{
	PhysXShape theShape(actor, shape);
	mPhysXShapeToRenderActorMap[theShape] = renderActor;

	renderActor->setPhysicsShape(shape, actor);
}