当我在firefox中使用inspet元素时找到joomla文件

I am new to Joomla and I am trying to learn things as I go forward. In Firefox when I do inspect element on my site, I can find the CSS tag that I need to change in order to get the result I want, but I cant locate the file that I have to make the change in. I am new to Joomla and I am trying to learn thi