Logos and css templates

Having spent (wasted?) a few hours fruitlessly trying to figure out how to modify the css blogger template to add a logo (my new "coffee-cat" picture, featuring one of my cats, plus a cup of espresso that I photographed before drinking it...) I have given up and changed my "profile" picture from a mug shot of me to my logo. I don't think I have enough time in the day to figure out how to hack the css...