How??

can someone explain to me how i can put pictures in the about me section on my profile page??? i'm scared to try it without some advice because i dont want to screw up my profile. i kno i have to do sumthing with either the CSS or HTML but thats all. and also..wats the difference between CSS and HTML on our profiles?? like once i got it once it will be a piece of cake i just need sum direction to go in. like where in the HTML box to put pic codes, or if i have to remove stuff.