Step-by-Step Instructions
1.  
Use the move tool () to drag out the rectangle and the triangle molecule.
2. 
Select the positive charge tool (), and click four times on a short side of the rectangle to add a charge of +2.0. Then, using the negative charge tool ( ), click four times along each side of the triangle, to add a charge of -2.0 in each place.
3. 
Use the duplicate tool () to make copies until you have six rectangles and two triangles.
4. 
Run the model and watch as your molecules form tetramers!