Adding side box

Would like to add a small box onto the side of my blog. Instructions here look good and workable, but I can’t seem to access the HTML of the blog. The theme I’m using is “Philosophy” and this blog came with my 1and1.com website.
The reason I want to put a box in is that people keep leaving comments, but I can’t access anything beyond the fact that somebody left a comment (I called the help desk on this more than once and their advice didn’t work), so I’d like to give readers some way of reaching me.