how do you get those characters and how do you select them

Well, if you want to get a sprite that's not from the Sprites Library, all you have to do is go to the button that looks like a file (which is to the left of the blocks, and below the Stage), click it, and choose the sprite/image that you want.

Here's a picture of the button that I was just talking about:



I hope that this helps!

With regards,

ErnieParke

You can also get images that you want to use for sprites off of the all mighty internet