Bootstrap theme

Hi. I’m pretty much a noob (1 month using it) when it comes to Yii, so sorry if this is a completely obvious answer. I have create a standard application with yii and I would like to add a bootswatch theme to it. I have checked forums, extensions, Yii documents and Google but what I can not really find is a straight forward explanation on how to do this and even if I can. Any help would be appreciated thank you.