You can access the workshop level by going to Extra Modes, then Somnasculpt Workshop. Inside this level, you can click on the water cooler to import a 3d model and place it on the side room's button to upload it to the workshop. You can also download someone else's model through the workshop and reupload it in order to get the achievement. If you are not contributing an actual usable model, it would probably be best to delete it afterwards so as to not flood the workshop.