You still haven't given a link or datasheet!
Some detective work (google image search) suggests that it is one of these
http://www.dx.com/p/ttl-to-rs485-module ... rN_4vnFLcs
This is a 5V device. The Pi can only deal with 3.3v devices unless you buy an additional logic level converter (or easier buy a 3.3V RS485 module).
Generally speaking, you should connect these modules to the TX and RX pins on your Pi.
However given that you aren't giving much information, it is impossible to tell you how to connect it.