Wiring a MC to a RXTX USB TO SERIAL

I got two MC's the ATTiny84 (7PIN) and the PIC16F877-20/p
&
USB to Serial as shown here.
http://guides.machinescience.org/mod/book/view.php?id=1316&chapterid=4897

here it shows that Pin 1 & 2 on the USB to Serial device is the RX/TX and connects to PIN 2/3 on the PIC16F877-20/p Microcontroller as shown here
http://guides.machinescience.org/mod/book/view.php?id=1316&chapterid=4808

but when I look up how to connect the USB to Serial RX and TX to this ATTiny84 chip, what the hell am I looking for? how do I know which port to connect the TX/RX?

http://www.atmel.com/dyn/resources/prod_documents/8006S.pdf

and do those also use the same wires to Flash the Chip with instructions?

How can I pull the instructions on the chip currently and read what is already on there?

Thanks! Many questions, Many