95 Geo Prizm wiring question

This is the first time I've tried to install a new radio, so bear with me if I'm rather ignorant...I'm trying to install an after-market radio/cd player in my 1995 Geo Prizm.  The wires coming out of the new radio are labeled things like "left rear +" (and "right front -", etc.), but according to your color code:

https://www.the12volt.com/installbay/detail.asp?info=alarm&year=1995-96&make=Geo&model=Prizm&ID=17886&type=Stereo

(sorry, I don't know your link syntax yet), all I've got in terms of speaker hookups is "Front Speakers 5" Doors, Rear Speakers 6 1/2" Rear Deck".  What do you mean by "5" Doors" and "6 1/2 Rear Deck"?  What should I attach to what?

Thanks for your patience!  Please ask me whatever else you need to know to help me.  Thanks for your help!