At present I seem to have placed the widget within the body of the post, which is not what I wanted; I would prefer that it come at the very bottom, after the social media links and the "labels" information. I found this information -
Modify your HTML template to add the code below at the place where you want the widget to appear: <div class="linkwithin_div"></div>- but I'm understandably nervous about even opening my template for fear of screwing something up (I minimally modified the blog format from a preset template).
It's also too small. I installed the three-thumbnail-wide version, then wanted to change to the five-thumbnail-wide version, but haven't successfully been able to alter it.
Most importantly, it's not currently linking to "relevant" past posts, which was my goal. It seems now to be linking to random past posts. My understanding is that it takes time for LinkWithin to "prowl" the blog and categorize the relevance of past links based on keywords. I'll give it a few days to see how it goes.