How do I know which slots to install my 2x 512 sticks in - Asus A7N8X

How do I get my memory running in Dual Channel Mode - Asus A7N8X

EDIT: Figured out my original question, so here is an updated one.

I got the computer up and running, I'm on it right now. However when the computer starts up it says that the memory is running in single channel mode.

I am running:

Asus A7N8X mobo
Athlon XP 2500+
Kingston HyperX DDR400 (PC3200) two 512 sticks 2.5-3-3-8
old vid card probably doesn't matter I'm sure.

Everything is stock, no OC yet.

I'm new to this so sorry if this is stupid, I'm going to go look in the bios for anything that might be obvious and come check back here later

try using both of the blue dimms.

got it, thanks. I installed it in the first and third DIMM slots and it now says it's running in Dual Channel, and my SuperPI 1.4 went down 1.5 seconds