Generally, fax software provides a printer driver, and you "print" to
that driver from the File - Print menu of any program that can print
(then it asks you for the fax phone number). That would include any
previously scanned pages, just print those page images.
Do you have Windows XP? If so, there is free Microsoft fax software
installed from your Control Panel Add/Remove Programs - Windows
Components. You can search www.google.com for XP fax for more
details.
You will need a regular fax modem (dialup variety) and a regular phone
line for fax.