How can I modify the parameters of a Wi-Fi network?

This is the same code as my other question link but this time I want to know how to connect to the Wi-Fi network and modify its parameters in the code there are two comments where they are concerned about questions

private final BroadcastReceiver wifiScanReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        if(intent.getAction().equals(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION))
        {
            wifiList = wifiManager.getScanResults();
            WifiElements wifiElements = new WifiElements(LoginActivity.this, wifiList, R.layout.wifi_items);
            AlertDialog.Builder builder = new AlertDialog.Builder(LoginActivity.this);
            builder.setTitle("Elija una red para establecer conexión");
            View v = LayoutInflater.from(LoginActivity.this).inflate(R.layout.wifi_view_ssid, null);
            builder.setView(v);
            ListView netList = (ListView) v.findViewById(R.id.lv_ssid);
            netList.setAdapter(wifiElements);

            netList.setOnItemClickListener(new AdapterView.OnItemClickListener() {
                @Override
                public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {

                    /**como decir que se conecte a esta wifi??? 1 duda*/

                    //despues de conectar satisfactoriamente muestra el dialogo para que entre user y passwd
                    showdialog(wifiList.get(i).SSID);
                }
            });

            builder.create().show();
        }
    }
};


//********************  SHOW DIALOG  *********************
public void showdialog(final String ssidWifi) {
    AlertDialog.Builder builder = new AlertDialog.Builder(this);
    builder.setTitle("Nombre de usuario y contraseña");
    builder.setMessage(ssidWifi);
    builder.setCancelable(true);
    View v = LayoutInflater.from(this).inflate(R.layout.login_show, null);
    builder.setView(v);

    final TextInputEditText textUser = (TextInputEditText) v.findViewById(R.id.user_name);
    final TextInputEditText textPassw = (TextInputEditText) v.findViewById(R.id.user_passw);

    builder.setPositiveButton("Aceptar", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
            if(textUser.getText().toString().isEmpty())
                textUser.setError("@string/error_field_required");
            else if(textPassw.getText().toString().isEmpty())
                textPassw.setError("@string/error_field_required");
            else
            {
                /**logica de la conexion, como establezco el proxy, user, passwd y el apartado omitir proxy para.  2 duda*/

            }
        }
    });
    builder.create().show();