Pretty simple, actually. First, you have to find or create the images for the monsters you want to add. Then, open the material base (press F10), and click on Graphics/Battlers. Click on "Import..." to the right, and find the images you want to add. When you add them, you want to left click on the ONE color you want to be transparent, and right click on the color you want to be partially transparent. (If you don't want a partially transparent color, right click on the same color you made transparent) Then, you want to open the database (press F9), and go to the Enemies tab. Fill out all the proper data for the monster, and remember to try to balance it with the character's power levels. Then, double-click on the image, and select the appropriate image from the list. After that, go into the troops tab, and set up the battle. I recommend you use the event options to make the battle more interesting than just attack, be attacked, attack again. Once you're done with that, you should have a battle that you can test.