So you want to make a Click To Speak game. Here's a quick guide to getting started.
First, open up TextEditor3. The first thing you'll see is this box:
The name of the player character goes in the box marked PC, and the name of the other character goes in the second box. You can choose to type in the character names now and click Save, or you can close the box without saving. You can open this box again at any time by selecting Edit -> Characters from the menu bar. For now, let's say our player character is named Alice and the non-player character is named Bob.
After exiting the character box, you're in the main editor: 
At the moment, there's only one space visible for a line of dialogue. This will be the first line played when a user starts the game. The drop-down box to the left allows you to assign the dialogue to a character. You can have either the PC or the NPC speak first, but the player only gets to do something when the NPC is talking, so let's have Bob speak first.