Alas…I got it up, now how do I do this?

I was initially very worried about installing my own blog to tinker with but the temptation was too great! I got it installed. It was a breeze.
Now, I’d like to modify 2 things but not sure how to do about it.
1) The current blog stretches over the entire page but I’d like to shoring it a bit to something the size of this forum.
2) How do I include a header graphic instead of having a text link for my title.
Appreciate your advice on how I can do that.
Thanks.
melvin