In order to install a theme, review the following guidelines:
* Download desired theme
* Transfer to PS Vita theme folder
* Open Theme’s manager app and look at the current themes folders in the install local theme option
* Look at the current themes. They should be listed as theme01, theme02, and so on. Make a mental note of this.
* Open VitaShell
* Go to themes folder
* Look for the theme you just downloaded and rename downloaded theme folder to the subsequent theme. For example, you’ll see theme folders with the following naming sequence: theme01, theme02, theme03, etc. In our case, our downloaded theme folder will need to be renamed to theme04.
* Exit VitaShell and open Themes manager
* Install the theme you just renamed
* Go to system settings -> themes and select your new theme
* Enjoy!