Hi, first of all, make sure that you have followed the plugin installation process completely. Please follow the steps as mentioned in the URL below in sections “Install a Plugin using the WordPress Admin Plugin Upload” and “Manually Install a WordPress Plugin using FTP”:
http://www.wpbeginner.com/beginners-guide/step-by-step-guide-to-install-a-wordpress-plugin-for-beginners/
Let us know if you have still the issue even after following the 2 methods above. Also let us know in detail in which step you are actually facing the issue, and the error message if any.