Pretty simple mate, make sure no one is using it to connect to the internet (or wired for that matter). Unplug router, let it rest for a few seconds, plug it back in again.
Sorry, probably made it sound more technical than it is (my router/wireless has no on/off switch)..
Wurzel
*also, when you installed and set up, did you set it up to connect automatically? That may cause it not to show on your list of wireless connections (no idea why, just seems to happen)*