i have a laptop asus M50S83Vn-SL

Intel Core2 Duo(Penryn) T8300(2.4G)
Intel PM45+ICH9M
2048MB RAM
320GB
DVD±RW
nVidia Geforce 9650M GT

i want to install snow leopard..
can i install to snow leopard right away or i have to install leopard first?
and which iso should i use?