If you go to the skins folder (by default Documents\Rainmeter\Skins) and navigate to the skin you want to edit, you'll see a .ini. Open it with notepad and look at the code to get an idea of what everything does. Make a backup, and then play with the values to see what happens. When you change a value, save the file and refresh the skin. That will apply the change. Just tinker with this for a bit and you should end up able to change it how you want.