Click "Search for an access point." (For information on the other option, using Nintendo’s discontinued Nintendo Wi-Fi USB Connector, check Nintendo’s site.
The Wii will spend a few seconds searching for access points. When it tells you to choose the access point you want to connect to, click OK. (If it doesn’t find any access points, you need to figure out what’s wrong with your wireless network.)
You will now have a list of wireless access points that you can scroll to. The list will show the name of the access point, its security status indicated by a padlock) and the signal strength. If the padlock is unlocked and the signal strength is good, you could actually use that connection even if it’s not yours, although some people consider it wrong to steal others' bandwidth in this manner.
Your access point will have either a name you’ve given it or a default generic name (for example, mine is just called WLAN, which is the type of security I use). Click on the connection you want. If it is a secure connection, you will be asked to input a password. After doing so you will have to click "OK" a few times to get to a screen where your connection is tested.