In Installer, select one of the hundreds of themes that you want, then touch the Install button. After it loads in, press the home button to shut down. When you come back on, the new theme will be there. Not every theme makes a major change. Many of the themes have a More Info section in their description that show what the changes will look like.
The Shift Key and punctuation keys are on your computer for a reason. Learn to use them; they make your communication more readily understandable.