Your model must be composed of closed watertight geometry.  Examples include 3D solids, closed polysurfaces (Rhino), solid group (SketchUp) or watertight mesh. (in Rhino use ShowEdges to confirm no naked edges)

NOTE: You cannot print open surfaces, 2D geometry, 2D text, or materials.

Eliminate non-manifold geometry (edges shared by more than two faces).

Scale your model to fit within build chambers limits (see printer specifications above).

Move your model to the world origin (0,0,0 of x,y,z).

Use Bounding Box (in Rhino) or similar to determine the overall size of your print.

Determine the overall dimensions in x,y,z directions and provide that information when you upload your print. (see image below)

Export your model as a STL (Stereolithography format) file.