Support modelling question

Hi,

I am in process of creating a Staad.Pro model for a structural steel module (with piping items inside it). The module is shaped like a cube with diagonal horizontal, vertical and diagonal beam members. Please find below sketch of the structural steel module. The sketch shows the module (in black box) "sitting" on another structure which interfaces (touches) with the module via those red horizontal beams (underneath and parallel to the module).

What is the best way to model the supports of the module? I am thinking of a distributed supports but it is not available.

Appreciate in advance your kind feedback.