Okay, you have to give us a little bit more detail than that for us to be able to help you.
What tablet is it? What's your wifi setup? Is it just the default modem/router combo your ISP rents to you? Who is your ISP - at&t, charter, comcast, time warner....
What happens when you try to connect to wifi? Does it give an error message? What exactly does it say? Are you entering the password for the wifi correctly, and are you making sure it's the correct network?