If you are installing plugin first time than upload plugin file in wp-admin following the path: wp-admin -> Plugins-> Add New -> Upload Plugins -> Choose the plugin zip file from your computer.
If You have already installed plugin than copy "custom-plugin" folder and paste it on this path : wp-content->plugins.
After successfully installation, You need to activate plugin from plugin lists.
After that you can see the configuration option in the left menu Redeal Configurations. Click on it.