Open the STL file in a 3D modeling or mesh editing program
Import the STL into the software
Convert the mesh to an editable format if required
Use mesh tools to move, scale, rotate, cut, merge, or delete geometry
Repair holes, flipped normals, and non-manifold edges if needed
Add or remove details with sculpting or mesh editing tools
Save the edited model in STL format or another supported format
Export the final file for 3D printing or further editing