Hi,
All the other disks can be installed after you install the Main FCP disk. Each disk has an install package in it that works. The only discs that don't are the LiveType content discs. You have to use same method MichaelLAX described just with a slight modification.
1. put the LiveType content disc1 in and in the terminal use:
$ sudo installer -package /Volumes/LiveType\ Media\ 1/Installer/LiveTypeMedia1.mpkg/ -target /
2.Once install is successful swap in the second LiveType content disc and use:
$ sudo installer -package /Volumes/LiveType\ Media\ 2/Installer/LiveTypeMedia2A.pkg/ -target /
G.