make smaller the font size

Hi again, I have bought Catch Everest Pro for my website, http://sercade.org/. I’m trying to make smaller the font size and I can't. I have already done it with the h1 size (as I have read adding #main h1 { font-size: 20px; }), but I need to do the same with: - the general content - the information about the date and the category where I have published the post - the last entries in the principal sidebar widget Thanks in advanced and sorry for my English,