If you’ve jailbroken your iPod touch or iPhone using any of the 1-click apps or major guides, you’ve been using an out-of-date version of Installer.app meant for version 1.0.2 of the iPhone to install your apps. Today Nullriver released a new version of their software with a fresh interface and is now v1.1.1 aware.

To update:
Step 1. Open your current version of Installer.app
Step 2. Go to the update section at the top.
Step 3. Tap the Installer update and tap install.

Everything should update and you should have the fresh new version of Installer.app installed, you can tell by the revamped OSX-esque icon. Also be sure to update your Community Sources to ensure you have a current list of all the apps available for your device.