To install Linux on a SPARC based computer, should be strightforward if you follow the informations provided by your distribution.
To boot from a floppy drive you have to have an install image on a
floppy disk and to issue the boot floppy from the OpenBoot.
If your computer does not have a CDROM or a floppy drive, you can always try
to perform a network installation using NFS as explained by
this French document:
http://www.linux-france.org/article/materiel/sparc-install/Sparc-netinstall.html
. Basicaly, you have to set up an NFS server and to boot your
computer using the
boot net vmlinux nfsroot=192.168.52.12:/tmp
in order to access the image that is exported by the
192.168.52.12 computer on the /tmp directory.
Another source of information, this one is written in English,
is this FAQ from the UltraLinux website (
http://www.ultralinux.org/faq.html#q_5_9
)