It depends on what event you're going to use. For example, Entity events: $event->getEntity()->sendMessage("your message here"); For Player event: $event->getPlayer()->sendMessage("your message here");
There is no sendMessage() method in the Entity class >.< check instanceof Player. Or well, it should depend on who you are sending to. After getting the player object, ->sendMessage("message") it. There are different methods to get different players in different cases. Read the docs for details.
uhh the $event here is the actual event's variable? like PHP: public function whatever(whateverevent $wee){} the $wee there?
Yes, but different events have different methods. You are a good observer. Continue studying other plugins and you gonna make successful plugins?