i wanna change my profile

i wanna change my profiles theme but i literally dont know how to css correctly? fi tried learning it but its so confusing? i wanna learn to do it, but im not to sure how, so if you see my profile looking strange, its probably cause i messed up! whoops

UPDATE can someone PLEASE TELL ME WHY THE BACKGROUND IMAGES I PUT KEEP BEING BLURRY EVEN THOUGH THE IMAGE ITSELF ISNT?

UPDATE 2: i DID ITT!! im satisfied for now