You need to purchase an external sound card or USB sound card, if you intend to use 5.1 output from your Laptop.
Or you can hook them in parallel using any splitter pin or just hot wire all connections to a single pin and use the setup as a two channel surround system. i.e you get the same stereo output from all the speakers
Else just connect the Green plug and you can use the setup as a 2 channel speakers.