After expanding the zip file,
drag each of these folders into your themes folder.
<br /><br />
ck_rollover_red<br />
ck_rollover_grey<br />
ck_rollover_brown<br />
ck_rollover_green<br />
ck_rollover_blue<br />
ck_rollover_colorful<br />
ck_rollover_orange<br />

<br /><br />
If you don't know how to install a theme,
read the documentation at 
<a href="http://docs.moodle.org/en/Themes#Installing_a_theme">http://docs.moodle.org/en/Themes#Installing_a_theme</a>.