BTW, they are using the software package called fritzing which is free and easy to use.
The capacitor is backwards in the image. The white stripe should be connected to ground. Swap the leads and it will be good. Connect the diodes as shown in my ascii-art below (I'm having a problem attaching images) for each of the leads of the motor. Do you have away to measure resistance like with a multimeter? If not, do you have a physically large resistor to limit the current to the motor. Can you tell us the colors/colours 
that are on the resistors.
12V __|/|__to motor__|/|__ GND
|\| |\|
Or check out page 2 on this PDF document. It's better than my ascii-art. http://www.ti.com/lit/ds/symlink/l293d.pdf