1. Click on BlackBerry | Install Signature Keys... menu item on the BlackBerry menu in Eclipse.
2. In the standard File Open dialog that appears, navigate to the location of the code-signing key files on your system. You will see three, but select only one for now.
3. Once the file is selected the Signature Tool Registration file is shown where you can enter the PIN and password that you provided when requesting the code-signing keys.
4. Once you've completed the registration for this key file, repeat the process for the other two files.
The registration process goes pretty smoothly assuming you can connect to the Internet and can remember your PIN and password. Be careful about guessing passwords if you can't remember them properly, as you can lock your account with too many wrong guesses. If that happens, you will have to call BlackBerry support at 1-877-255-2377 to request help with resetting the password attempts and or...