page-template specific css/theme

hello,
i am making a website which have multiple sets of pages. i seperated them using the page-templates. now i want to customise each set of pages using css file. how do i change that? . i am using twentyfourteen theme.

i found the below given post but there is no such code in header.php of tweentyfourteen. in new themes how do i achieve the same result.?

sorry if this is already addressed. please give me the link

http://ww.wp.xz.cn/support/topic/how-to-have-a-separate-stylecss-for-each-page-template?replies=11