Add CSS Link Node to Head

I was having some jquery problems with a plugin. At first I thought it was the fault of the theme, but when I ran a javascript console diagnostic, it showed that the bootstrapper file was not filed correctly. Here is what the console churned out:

Link node bootstrap.min.css should be moved to the document head in completefirstaid.net

I’m not quite sure where the Head is located in WordPress or where the link node should be placed once I find it.