Change from WAP to WEP security for DS Games

Hello,

I'm trying to switch my routers security from WPA to WEP so that I can use my DS games online features. I am as far as having the CISCO admin page open so that I can see Setup/Wireless/Security/AccessRestrictions, and so on. I just don't know exactly what to do from this point (If I even need to be this far into my router's information and security.

can someone please help? Thanks!

EDIT: more specifically, I'm trying to do this on a 3ds XL.

The 3DS XL should connect to WPA or WEP encrypted networks.What model is the router?
What happens when you search for a network using the 3DS internet search feature?

To change the router security once in the management portal go to:
Wireless Tab->Wireless Security-> then you can change the Security Mode