HTML troubles

Well, I officially waisted an hour of my life. I was trying to add a column to my blog making it a 3 column template. I found instructions, but they were for fresh blogs without any content already. It did split into 2 in the preview, but it looked really horrible and the middle was at the bottom, lol. So, if anyone know how to make a 3 column page after your page already has lots of stuff on it feel free to email me! I'd love some help! :)