If you have any questions about iSpirit, please read the iSpirit FAQ's documents first. You can also get help by visiting our Blog.

1. The easiest way to install theme on iPhone is by using iThemeSky App or iSpirit.
» How to download & install themes with iThemeSky App on iPhone/iPad/iPod Touch
» How to download & install themes for iPhone/iPad/iPod Touch with iSpirit from computer

2. Manually Install
   (1). Connect to your iPhone (with iSpirit or other way)
   (2). Drag & drop the theme folder to "/Library/Themes" – alternatively, you can copy the theme to "/private/var/stash/Themes…" or "/var/stash/Themes…"
   (3). Launch Winterboard and apply the new theme as usual. done!

» View complete theme installation guide here

Please follow our WinterBoard install & use guide here.

It cite some of the most compelling reasons to jailbreak your iPhone here.

Please follow our guides:
» How to jailbreak iOS 5.1.1 Untethered with Absinthe 2.0 on iPhone 4S, iPad 3 and more
» How To Jailbreak iPhone 4S on Windows (iOS 5.0 & 5.0.1)
» Jailbreak iOS 4.3.1 untethered with Redsnow 0.9.6.

Some themes require additional apps to work perfectly, read more about that here.