The Drupal BMLT plugin has just undergone a radical rewrite. All three of the CMS plugins now share a common code base, so they present exactly the same administrative interface as each other.
First, fetch either the Drupal 7 module from the Downloads page. This will bring a ZIP file onto your computer, decompress this file, and rename the resulting directory to “bmlt.” Install this in your sites directory. Once you have the module installed, go to the BMLT settings, and read this page for guidance on administering the plugin.
NOTE: You should always use this zipped file, as opposed to directly fetching from Git. That is because the project contains Composer Dependencies, You would need to do a `composer install` to get all the required dependencies.
Once the module is set up, then read this page to get guidance on how to make the BMLT instances appear in your articles.
You may also want to look at these pages for ideas and examples. They demonstrate WordPress plugins, but the process is almost exactly the same for Joomla! and Drupal.