If you're only getting sound from one speaker, then either there's a connection problem, or a fault with the speakers somewhere.
The input cable you want to use, is the 2x RCA/phono plug to 3.5mm jack.
Here's a 3m one, if the included one is too short.
Check the connections. You are using the spring clips for the left speaker, and not the centre one by accident? Also, do you have the RCA plug connected to the left channel input, and not centre by accident?
If the cable are connected to the right sockets, check the speaker cable connection from the subwoofer to the left satellite. Make sure the polarity is the same both ends and that the copper wire has a good clean contact within the spring clip. Maybe the plastic sheath has been pushed inside?
If all that's fine, then another possibility is that the included input cable is faulty. If you still get sound from only one speaker with a new one, the only other conclusion is that the speaker themselves are faulty.