Click on the Text Tool (to the right of the Pen Tool) in your left-hand toolbar. You'll see that your Properties tab changes to let you set your text properties; text type (leave it as Static Text for now), your font style, font size, font weight, alignment, space between characters, and space between lines. It's much like Microsoft Word or any other rich text editing program; you've probably done similar things when customizing your fonts in chat rooms.
An easy-to-read font is best, depending on your purposes; for graphical effects, highly stylized fonts are fine, but for regular text a clean, crisp font like Arial or Times New Roman is recommended. For something like this, though, we can get a little bit more creative; fonts like Comic Sans are good for character animation, because they have a bit of a handwritten feel, rather alive, a bit playful--but they're still clean and easy for the eye to discern. I've chosen "Calvin", a handwritten font with a slight flair and a comic feel.
Because my background is black, I've set my font color to white. Get creative with your font colors--blue on white, white on red, anything your mind can think of. There's no reason to stick within conventional boundaries unless you're doing professional work; don't try to imitate the way you think it "should" be. Play with your own style. (Just try not to blind us. Neon orange text on a neon green background may just be a bit over the top. Not to mention painful on the retinas.)
