Installing new memory

Got a new iMac with the standard 2 x 2gb RAM and then bought 2 x 4GB RAM from OWC.
When I install the new cards do the pairs go side by side or front to back?

I believe the 2 x 2GB will be side by side so I'm thinking that the new 2 x 4GB should just go in the other side by side slots, but wanted to make sure that was right.

Thanks!!

Your iMac comes with two memory banks: Upper and Lower, the lower being closest to the removable screen. Always insert them in matched pairs, that is, side by side in the same bank. One bank is already populated, just put the new modules in the empty bank.