get legal copy.......no worries, not much $$ on ebay or buy locally
bogartin allowed here notta
a) Turn on mac, just to get power to optical drive
b) open optical drive
c) insert CD/DVD
d) turn off mac
e) start-up mac while holding down the "c" key
f) once start-up is complete, you should be at the installation screen
g) choose new install w/wipe the HDD
h) let it do it's thing
i) when finished, reboot from HDD and remove CD/DVD