First of all, make sure you have the latest version of Code Snippets installed and activated. If Code Snippets is not yet installed, you can find installation instructions available on the WordPress.org plugin page. If you already have Code Snippets installed, make sure it is up to date by visiting the Dashboard > Updates page of your WordPress admin.
Code Snippets Tags can be installed just like any other plugin. Visit the Plugins > Add New administration menu and search for “Code Snippets Tags” in the search box. Click on the install link under the “Code Snippets Tags” plugin, and activate it on the next page