1. Click the Theme app to open the MIUI theme store.
2. Now you will serve with so many theme on that apps. You can choose the theme based on the popular one or a specific category. Choose one of your favorite theme, click on them and then click the Download button.
3. If the download is completed, you have to switch to the Local tab just like shown as the image below. When you go to this tab, it will showing your theme collection (theme that you’ve been download before). Yes, it means you can download and save more than one theme on your device. Now just choose one of them and then click Apply button.
4. Wait for a while and.. Tada! Your theme has been changed!
Please note that if you don’t like some components on the theme style (such as the lock screen style, nav bar, etc.) you can easily change them with the components from the other theme. See how to do it on this link (coming soon).