How can i create custom level for Lyra demo?

Lyra have some procedural mesh.
But these meshes are white box, they don’t have material.
So, i don’t know, when i want to make level then how to do that?
what is this workflow?
make white box or procedural mesh,then place to world for make custom level, then replace material? or export these mesh to substance painter for create material? or export mesh to 3d model software for create mesh details?