This plugin displays your www.eventish.com events list in your WordPress based website as a sidebar widget.
You only need to log in to WordPress admin panel, activate the plugin in "Plugins" section then proceed to Appearance -> Widgets to drop the widget to sidebar. After, you need to enter your info to receive events from eventish.com.
API Key is your unique key generated by http://www.eventish.com event management software. You need to go to http://www.eventish.com and register there if you still don't have an account. Afterwards, you can find your API Key in your "My Account" section.