extend, installation

Hi everybody, first time here. So anyone has a tip in the following thing: I tried to install new modules under “Extend”, but drupal doesnt do it. no error message, just goes back to “home” The module I wanted:https://ftp.drupal.org/files/projects/devel-8.x-1.0-alpha1.tar.gz my version is Drupal 8.1.9. Thanks[…]