"extract it" --> Unzip the Installer.zip file onto your desktop. It should be in a directory called Installer.app, or similar. The directory should contain a whole load of files.
"upload it to your iPhone using SSH" --> You are going to have to SSH into your iPhone, (search) and upload the whole Installer.app directory into your Applications directory. You will see other directories in the Applications directory which match the installed apps on your iPhone.
"Fix the permissions" --> You will upload the Installer.app directory on your iPhone using the "root" account and priviledges. You need to change these to "mobile" user so that you can run the Installer.app using your iPhone.
In terminal (search) you need to :
chown -R mobile /Applications/Installer.app
chmod 0755 /Applications/Installer.app/Installer
(OR: chmod -R 0755 /Applications/Installer.app)
That should do it ... or you can just run iLiberty+ again and this time choose Installer instead of Cydia ?!?!