Hello, you should be able to locate bluetooth devices on your Android device in the settings. You will firstly need to turn on Bluetooth on your Android so that it can search for Bluetooth devices. Equally, your bluetooth headphones will need to be turned on. Your Android should now automatically pair with your headphones.
However, if your headphones are running a newer version of Bluetooth (ie.Bluetooth 3.0), and your Android is only compatible with Bluetooth 2.0, you will be unable to connect the two devices together. The Bluetooth of your phone would need to be at least 3.0.