Each single piece of wire has two individual cores running through it. You remove half an inch or so of the plastic cover from each core on each end, exposing the bare wire.
You attach one piece of wire (2 cores) to each speaker, one core to each terminal on the speaker.
The other end you connect to the amplifier, again one core to each connector.
The back of the amplifier should show L and R for left and right speaker, two connectors for each speaker.
The connectors are often shown in red and black. Make sure you connect the black connector wire on the speaker to the black connector wire on the amp or the speakers may be out-of-phase, giving a slightly fuzzy sound.
To help you often speaker wire has a black line running down the outside of the plastic, down one of the cores.
This is so you can identify the correct core to put on the corerect connector (red or black). It can go on either red or black, but as I said, must match up.
This is one of those things that is easy to do but difficult to explain, but I hope I have made it clear in the text above.