How to Install Ninja Popup?

Automatic Plugin Installation

To add a WordPress Plugin using the built-in plugin installer:

    1. Go to Plugins > Add New.
    2. Type in the name of the WordPress Plugin or descriptive keyword, author, or tag in Search Plugins box or click a tag link below the screen.
    3. Find the WordPress Plugin you wish to install.
      1. Click Details for more information about the Plugin and instructions you may wish to print or save to help setup the Plugin.
      2. Click Install Now to install the WordPress Plugin.

Go to https://codex.wordpress.org/Managing_Plugins to learn about manually installing plugin.