From the assembly editor menu, please select File -> New. BW Tools will display a dialog asking for a template. The combobox "Type" should display "Thing". If not, please change it to do so. The list box contains a list of available templates and one special item: The 3DS importer. This is a special tool, useful for the importing of full 3DS model files. You will not need this tool if you are just creating a thing out of simple 3DS objects.
Double-click on "Thing Using a 3DS File" to select it. The assembly editor will load this template into its editor and do an automatic "Refresh". You should see a textured head mesh. Left click and drag to inspect it. Use the middle wheel (or the up and down keys) to move it closer or away. Double-click to return to the initial view.
Our thing has just a single subpart, named "_0".
Now find the line stating "ROT 0, 45, 0" and change it to "ROT 0, 0, 0". Click on the menu command "Refresh!" to see your changes.
Then add the following lines right under line with "PAINT..."
_1: SCALE 0.2 0.2 0.2
POS 0 37 -45
PAINT DIFF 1 0 0 SPEC 1 1 1
Do a "Refresh!". We added a second subpart to the thing...
Select File -> Create As to create and save the final thing. But caution: This will not save the assembly text itself! If you wish to save the text, select File -> Export Text...