SideNotesIM is installed on each computer that needs to communicate with other SideNotesIM users. The software is licensed per location, not per computer, but all computers in a location should have the site license in place in order to function. Locate the Download button under the Customers page.
If you have computers that do not have access to the internet then you can download the installation program to a shared network drive, removable USB memory key or simply burn it to a CD. Then run the SideNotesIM installer on each computer.
Sometimes during Windows installation, a workstation may need to have its permissions elevated. If you see an error when installing, right-click on the SideNotesIM installer file and choose "Run as Administrator." You also may need to uninstall and then reinstall SideNotesIM under an Administrator account on that workstation. Be sure to run SideNotesIM at least once under the Administrator account.