Please help an HTML-Challenged Blogger

I'm trying to stick a banner on my blog, and with this version of blogger it ain't easy, so if anyone out there knows exactly where in the html code I should go to tweak the margins, I would be forever indebted. I already tweaked it some, but now I am stuck, stuck stuck. What I did so far: Added the picture I created with Photoshop (and a photo of my knitting; resized to 750 pixels wide) using the Add Page Elements feature. Moved that to the top below the title, then changed the color of the title to match the background (don't want to remove the title so it shows up in search engines and anyway, can't remove it). Changed maxwidgets in header wrapper from 1 to 2 in the html code, and that's where i am. I checked a few forums and no one' directions match the code I see. Maybe I'll just learn to live with the cock-eyed banner.....