All backends are disabled

Hi all.
Need help pls. I install icinga2 and icingaweb . And i have a host problem
" * Error

All backends are disabled

#0 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Backend/MonitoringBackend.php(76): Icinga\Module\Monitoring\Backend\MonitoringBackend::loadConfig()
#1 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Backend/MonitoringBackend.php(214): Icinga\Module\Monitoring\Backend\MonitoringBackend::instance()
#2 /usr/share/icingaweb2/modules/monitoring/library/Monitoring/Controller.php(29): Icinga\Module\Monitoring\Backend\MonitoringBackend::createBackend()
#3 /usr/share/php/Icinga/Web/Controller/ModuleActionController.php(28): Icinga\Module\Monitoring\Controller->moduleInit()
#4 /usr/share/php/Icinga/Web/Controller/ActionController.php(154): Icinga\Web\Controller\ModuleActionController->prepareInit()
#5 /usr/share/php/Icinga/Web/Controller/Dispatcher.php(59): Icinga\Web\Controller\ActionController->__construct()
#6 /usr/share/icingaweb2/library/vendor/Zend/Controller/Front.php(937): Icinga\Web\Controller\Dispatcher->dispatch()
#7 /usr/share/php/Icinga/Application/Web.php(300): Zend_Controller_Front->dispatch()
#8 /usr/share/php/Icinga/Application/webrouter.php(99): Icinga\Application\Web->dispatch()
#9 /usr/share/icingaweb2/public/index.php(4): require_once(String)
#10 {main}"

what i must to do ?

sry for my eng

From the menu, head to Configuration -> Modules -> monitoring -> Backends (Tab) and enable the backend.