My dsi won,t update

Hello, I'm sombody, some of my friends have this thing called +internet or dsi +internet or somethin. one ov my friends bought his with it on his dsi, another just updated his dsi and got it, when I updated my dsi it said that my dsi was up to date but I still didn't have it, can anybody help. p.s. I don't know whats on dsi +internet or whatever it's called, so if you could help me with that to, I would like it.