Does your wireless ADSL router have security or encryption enabled on it? If this is the case, you must ask whoever has the security key to give that to you. If it is MAC Address restricted, then you must enter your Wii's MAC Address into the router's MAC tables, and then your Wii will be able to access the wireless access point.
However, as your Wii is not even able to detect the network, I'm not positive that either of these two situations is the case. What other information can you give us about your access point?