How do you install a scanner on a mac operating system

A lot of scanners are supported in Mac OS X - you plug it in & go. If it doesn't just work, you're going to have to install a driver. With a newer scanner, there should be a Mac OS X driver on a CD that came with the scanner.

With an older scanner (or if you don't have a driver CD), I'd check first on the vendor's web site to see if there are drivers for Mac OS X that will support your scanner; if not, you can purchase VueScan which will work with most scanners.

If you're running Mac OS 9, you can download an older version of VueScan from VersionTracker.