NEEDING SOME HELP STARTING OFF IN RPG MAKER 2003?

So my game is going to run on RPG Maker 2003. My problem is mainly with the sprites. I've created a field sprite and a battle sprite. Problem with the battle sprite is, I don't know how to change it from the default ones you select. (There's a drop down menu with default ones.) The field sprite seems wrong all together. I made a feild sprite at that charas project website. But when I import it in a RPG Maker, its too big. (The defaults are "char1" and my sprite is way bigger than the ones on that one. I've been looking for a solution for a while now and I hope you guys can help me out. Thanks!