how to install .jar files on BlackBerry phones. Installing .jad files on BlackBerry phone is easy. and you can use pc to install.jar files on BlackBerry phones. Firstly you should download .JAR files to your PC and connect your Blackberry to your PC via the USB cable, then open “Computer” in the Start Menu, and go to the folder/location on your PC where you stored the .JAR files, copy the .jar files into the root of Blackberry or a subfolder, then unhook Blackberry from USB cable. In the applications on your BlackBerry phone ( or on home screen depending on Theme) scroll to the “Media” icon > Click the “Media” icon to launch it > Press the menu button and select “Explore” > Locate the .JAR file either on the device memory or memory card (check both as the Blackberry seems to just sort of stick system memory and card memory together) > Click the file, and it should prompt you to download and install > Click “Download” and you will begin to install .jar files on your BlackBerry phones.