To install the plugin you need admin access to your Wordpress website. If you don't have access, you will need to ask your webmaster to grant you access.

Specifically, you will need permission to install a new plugin - if you don't have access, your webmaster may be able to install it for you.

To check if you have access, login to your website back end, and on the left hand side where the menu is, look for the plugin menu item:

If you can see this menu item, you can install the plugin. If not, contact your webmaster.