ds lite: conectivity issue

I'm trying to connect to my wireless home network with my ds lite, but when I try it sends me a pop-up that says "the access point's security settings are not supported by the nintendo ds. For help, visit support support.nintendo.com" what can I do? this maybe my only chance to get the shiny suicune to unlock zoroark on my pokemon black, and I know, I can do that with pokeav, but I wan't to do it the right way ( no offense to cheaters XP )

The DS doesn't support WPA security (which most use these days). You need to have no security (not recommended) or WEP security (not really recommended either)...Depending on where you live, proximity of your neighbors, and how vigilant you are with your home wireless network, it may or may not be wise to use WEP.

but how do I change it, I could change it to wep and back to wpa as soon as I get the suicune if I just knew how, please, tell me how to

Depends on your wireless router. You need to connect to it and then change the settings.