Open the Settings menu on your Android device. For most Android devices, you can access Settings from the pull-down menu. Some editions may require you to pull the menu open twice to fully extend it. You can also access Settings from the app tray.
This process will work for most Android editions. Samsung Galaxy devices have a different location for the network settings menu (listed below).
Go to System > Advanced > Reset options > Reset Wi-Fi, Mobile & Bluetooth.
Samsung Galaxy devices
Samsung Galaxy users need to go to General Management > Reset > Reset network settings.
When you're ready to start the reset, tap Reset Settings. You might be prompted to enter the passcode for your phone--if so, enter it. Choose Reset Settings one more time to wipe your network settings.
After the network settings have reset, everything from Wi-Fi to Bluetooth settings will be gone. Restart your phone. When it boots, you can try connecting to a network.