Enabling plugin language

Hello.
I just installed a plugin on my WP theme. I need to change its language for the front-end side. The language that I need is already in the plugin’s language folder. I just don’t know how to activate that language or the changes that I need to make in order to make the plugin to use and display that language. I have read many documents and they seem to refer only to language changes on WP theme but not on plugins. Any help? It will be greatly appreciated. Thanks!!!!!