On the login screen you can choose Play or Editor. If you select Editor, it'll take you into the screen for choosing your map and to begin.
Triggers can be used for alot of things. On click triggers on people can make someone talk, for example. Area triggers can spawn creatures or make you go to another scene.
If you need any help with triggers, gimme ayell. But I suggest just poking at it til it works cause really that's all I've done.
