In a stereo setup since you want the left and right channels to be identical you would connect one of each in parallel on each channel. That would give you a 4 ohm load with a max power of 13 watts into 4 ohms,
If the amp has more power than they can take at the impedance the hookup of the speakers creates then it won't matter how you hook them up.
If the amp is less powerful than the 26 watts they can handle then how you connect them will depend on what minimum the amp will tolerate before shutting down or blowing up. You want the configuration not lower than that minimum
You can figure it out here
http://physics.bu.edu/py106/notes/Circuits.html