http://store.auctiva.com/BarbsLamps
In the top right corner there is a blog tab.
You can also purchase a domain on our stores tab so that it could be something like: http://barbslamps.com
Some of the ways that people may find your blog include your inclusion of your store URL in your winning bidder emails, feedback thank you emails, and other communtications you have with your buyers. Your me page would be a good place to promote your store url.
You are also hoping that Google finds and indexs your blog entries so that when people are searching google for items similar to what you sell they'll find your blog. Hopefully if your blog is something they are interested in they will come back to read it as you post new entries because it's an area they have interest in. That provides you additional chances to market your featured items and other items in your store.
When writing your blog entries think of things that may be of interest to those buyers. Even a blog a week that is a paragraph or two of quality info or thought is enough to gather interest.