Need help with Messages/Dialogue.

I'm new to RPG Maker (VX Ace), I've set up all of my characters, weapons, armor, etc. but I really haven't began making the game yet. I'm going to start by testing out the XS message system I copied Into the game so that I can see how that will look, but no matter what I do I can't seem to spawn another character to talk to let alone figuring out how to set up a message.

Any help would be greatly appreciated.

Also, I have a slightly off-topic question: how do I size the map I'm making to fit the entire window aside from the tileset box?

The picture below may help. 

That's the largest size you can make your map.  You'll see on the toolbar you've got 1/1, 1/2, 1/4, 1/8 - those are the only zoom levels available.  The default size will fill the window when you play the game.

To add an NPC to talk to, you need to create an event, give it a graphic, and give it commands.

Please take a look at the starting guide for beginners, in my signature, to go over some of the basics - that should at least get you started.  If those really basic things elude you, I'd really stay away from scripts for the time being.

Okay, thank you for finding me a reference.

That's a shame, because I've seen games made by RPG Maker (or at least I assume it is) that have much larger rooms, I thought there was something I was missing.

I think your question was taken as, can you zoom in. If you're looking to simply make a larger map or room, right click on the MAP001 in the bottom left window. It's the one that starts with your project name at the top; "The Trials."

A dropdown window will pop up. Select Map Properties. The Width: and Height: properties allow you to control how many tiles you want it to be - as well as the backdrop for your battles, background music (BGM) and background sound effects (BGS) that play when the map is loaded, and map looping or background pictures.