How do I change my wireless network to WEP?

I'm trying to get wi-fi working on my nintendo ds but my wireless network is WPA and nintendo won't let you connect to WPA networks.So I need help changing it to WEP.How do I change my wireless network to WEP?
You need to connect to your wireless router and change the security settings from WPA to WEP. Usually, you access your router by typing in its IP address (e.g. 192.168.0.1 OR 192.168.1.1) into your web browser. You will need to know the administrator password to get into your router. If you don't know it or don't remember it, you could reset your router to the factory default settings and use the default admin password to get in. Hope this helps!