How do you set your Intel iMac to use 802.11n?

I had to replace my router, and I picked up the D-Link DIR-655. How do I set my 2ghz iMac to use 802.11n.

When I go to Network settings, there is no mention of what mode the connection is. I've checked every tab in the advanced settings.

This will be set on the router, not on your computer. There is no setting that I have seen in System Preferences for this.

In the router, go to Settings - Wireless Settings - Manual Wireless Network Setup - and on this screen you will be able to set the 802.11 mode.

Under the info tab in Network Utility you can verify if your iMac supports 802.11n ...

It should already be on n. You should not have to change any settings to "turn on n."