Welcome to the forum.
Do you have the manual for your Onkyo receiver? If you do, it's probably a good idea to read it in it's entirety. Page 13, however, begins the section on hooking up all your sources and speakers.
If you don't have the manual, try this link. A quick google search should lead you to a pdf download for the manual.
http:// http://www.onkyousa.com/Products/model.php?m=TX-SR600&class=Receiver
When the link opens, click on downloads.
If you need cables or speaker wire, you can order online from monoprice or just get it all at wal-mart.
As far as your speakers go. The center channel is, well, the center channel. It goes directly center usually under your display.
The AR towers go in the front left and right position.
The Def Tech bi-poles are for your rear surrounds.
Your receiver has a "rear height" channel. For basic surround, ie 5.1, you don't need to use this channel.
You will notice a subwoofer output mentioned in the manual. This is for a separate bass speaker, the ".1" in 5.1.
At some point you will probably want to add a subwoofer, but we can save this for a later discussion.
Hope this helps. If you have any further questions, feel free to ask.
