Aleli,
for changing the look of Moodle, you have to use themes.
themes can be found in plug-in section, link below
https://moodle.org/plugins/browse.php?list=category&id=3
With every theme, its mentioned the Moodle release, the theme is compatible with, as Moodle 2.8 is quite mature to support most of the themes that have released/revised in last 2 months, all you have to do is, download theme, and upload it to your Moodle > Theme folder, and then log-in as admin, and you'll see automated wizard running you through the theme installation.
once theme installation is successful, you can simply go to Administration>theme>theme selector and choose the recently installed theme.
while its been said, on windows installer package, the themes MAY not work, for everything to work as it should, ideally the moodle is installed on a live server.
while you want to test different plug-ins and themes, I would suggest making an account with gnomio.com (its of course free) and they will give you access to a free moodle installation with almost all the popular plug-ins and themes to play with.