That is usually at Documents/My Games/Tabletop Simulator/Saves (see Save Game Data Location). Place the save file in this folder, keeping in mind whether you already have a save of the same number or not (they can be renamed). Save files are complete as is, with everything already included.

Does tabletop simulator save progress?

Saving. Click Create at the top of the menu, and enter a name for your save. Click Save once finished.

How do you save items on tabletop simulator?

By using the in game "Stage" item you can save all objects currently on stage into a bag. Simply create your dungeon and clear the stage of any other objects (Make sure your dungeon is locked!!!). Then, go to the stage card object and click the bag icon. You can then save this bag as a "Set_" file.