First ensure that your processor is 64-bit (I believe most Intel processes are these days). Then ensure you have a good connection to a DVD drive (you can use an internal drive, if available). Insert DVD to drive. Install icon should appear on desktop. Double click icon and follow on screen instructions. If this process does not work, you can also boot directly from the install DVD, run some necessary disk utility operations, and then perform the install. However, I recommend first trying the icon install. If that fails, we can look at booting from the disk itself.