Use your browser to inspect the elements. If Opera Ctrl + Shift + I (same in Chrome). You should know CSS, this will help you understand how to manipulate the elements. If you don't I recommend to follow a free course here:
www.w3schools.com.
Everyone who knows CSS will modify easy fonts, position, colors, ... And there is a great tool for inspecting in all browsers. Just inspect the elements and note where and what to change. For changes inside a CSS file use a text editor. I recommend making a backup of the original tags (you can comment the lines and write a note to find it easy with Find command - e.g. MYMOD)