Short answer: Link back to your profile page.
Page Rank is fairly simple. It's a measure of how many links you have coming to your page and how powerful those links are. Google's search algorithm is much more complicated in terms of what helps you rank for a specific search query, but page rank still follows the same general principal of more links = higher page rank.
That being said, a good way to improve PageRank and linking to your hub is to participate in the HubPages community. Every time you answer a question, leave a comment on a hub, or post in the forums, you're creating a link back to your profile. These links are dofollow, and they come from other subdomains. By being extremely active, you're creating a dense network of backlinks from other HubPages subdomains to your own subdomain.
You could also look for links elsewhere, which would not only raise your PageRank but help you rank better in the SERPs. Quality can often be better than quantity, and getting a single link from a high PR site (PR 6 or 7) will do far more for your PageRank than a ton of links from PageRank 0 or 1 sites. You could try finding high pagerank sites that accept guest posts, and firing off a query letter. You might get turned down, but if you've already written the article you can just publish it on HubPages anyway. So why not write up an article and go searching for a home for it...?
At the end of the day, though, just find some more links. There's not much more to it than that.