(XOOPS 2.0.15)
$xoTheme->addStylesheet('home.css');
(XOOPS 2.2.4)
$xoopsTpl->assign('xoops_module_header', '.XOOPS_THEME_URL.'/'.$xoopsConfig['theme_set'].'/home.css" />');
You don't need to add any code to your theme file.
$xoTheme->addStylesheet('home.css');
$xoopsTpl->assign('xoops_module_header', '.XOOPS_THEME_URL.'/'.$xoopsConfig['theme_set'].'/home.css" />');