To install the mod you will need to place the two files in located in the .zip file into your Workshop folder.

This folder is located 

"C:\Users\username\Documents\My Games\Tabletop Simulator\Mods\Workshop"

Or in

"C:\Program Files (x86)\Steam\steamapps\common\Tabletop Simulator\Tabletop Simulator_Data\Mods\Workshop"