Just use the indicator – or better still, just drag and drop onto the share-box. Simple!
Get the deb from Launchpad
Save it to your Downloads folder.
Install the prerequisites:
sudo apt-get install libqjson0 libqxmlrpc1
Then install the deb:
sudo dpkg -i nitro*.deb
Fire up the dash and search for “Nitroshare” and follow the wizard. Repeat this for your other computers.
Heck – those computers can be virtually any distro e.g. fedora, mint, arch. Even Windows and PowerPC are supported.