How does the Toys "R" Us work Arceus event?

I wondered how the Toys "R" Us works Arceus event. I I know I use the mystery gift, but you have to have wifi for that to work? In my DSi, I sent to my home wifi Internet. To get Arceus, Toys "R" Us, what is exactly what I do? Can anyone give me a detailed explanation? Thank you!

You Go to your toys r us of 7 local November through 15 years and to be downloaded manually or by you in the store or you can download it via wifi by selecting Mystery gift from the start menu and select gift to get through wifi. Just make sure your set up a WiFi connection on your Nintendo DS.

Jesse and Bitty in Toys R US 3