Welcome to AndriodForums, sorry you are having a problem with your WiFi. I will try to help you to the best of my abilities
In order to set up a WiFi network, follow these steps:
1.) Open your app drawer, and click on the Settings app.
2.) At or near the top of the list, it should say WiFi, with a button next to it (on and off)
3.) If the button is reading off, tap it to turn it on.
4.) Now tap on the word WiFi to open up the list of WiFi hotspots that are in range.
5.) Select the WiFi hotspot you wish to use, and if asked, provide the access code for the hotspot.
6.) Tap Connect, and your phone will connect to the WiFi hotspot.
If this doesn't solve your problem, I would suggest registering for a free AndroidForums account as I am sure you will find plenty of information regarding WiFi troubleshooting