Tips on fixing wireless network problems
Hardware and software problems
If you use laptop make sure that wi-fi is enabled in it. Laptops frequently have button which can enable/disable wi-fi.
If using Windows operating system then go to Control Panel->Network and Sharing Center and click on Change Adapter Settings. Look through network connection icons and see if any of them have "wi-fi" words. If yes then make sure that these icons are not greyed out. Also check 192.168.0.1 IP address.
When setting up your home network make sure that you don't put your router next to appliances working in 2.4Ghz range. Appliances like microwave oven, remotely operated garage doors, baby monitors, cordless phones can interfere with wi-fi signal and prevent you from connecting to your router.
Also if walls in your house are built from brick, plaster, metal framing it is possible that your router signal could be reduced by these materials. Typical range of the router is around 100m but this can be significantly reduced by certain construction materials.