There should be a "In the beginning" for source, Id be willing to write it too =)))
1. Click on the light bulb thing in the menu to the left.
2. From the new list that has appeared to the right, click the dropdown list under "objects" and find prop_physics.
3. Click a place on the grid.
4. Right click the green box and hit "Create object."
5. Right click the newly made entity and select properties.
6. In the properties, go to "World Model" and click browse.
7. In the model viewer now, click (in the left box), props_c17, or props_interiors.
8. Scroll down the list of props in the right box now (I reccomend arrow keys) and select the furniture you want.
9. Hit OK and exit.
10. Hit apply, and then cancel.
11. When back on the grid, click on the entity twice. (4 circles will appear around it).
12. Drag the circles to rotate the model you've used to the desired position.
13. Move the rotated prop into the position you wish it to be in through the top, side, and front views.