So ...

Upon activation, you'll notice a new Envira Gallery menu item in your admin menu. Go to Envira Gallery => Add New to add/create your first gallery:

You can simply drop your images or you can use the available buttons. The "Select Files from Your Computer" button will allow you to manually select the targeted files from your computer or other connected external sources ... The "Select Files from Other Sources" button will take you to your Wordpress media library ...

The uploaded images will be displayed in your current gallery:

Next, you need to select the "Config" tab to configure your gallery settings. Each option is very straightforward ...

And that's it ... Once you are happy with your choices, click the "Publish" button.

Here's the newly published gallery and the automatically generated shortcode:

Now let's see the magic ...