Actually, taking another look at your site, it looks like the image is already set to float left inside of a paragraph. So if the paragraph is short, like the one you currently have (1 line), you will only seen one line floating there and the next paragraph below it. Try making a longer first paragraph and you should see that it wraps.
The reason why the next paragraph stays below the image instead of wrapping is because your stylesheet (~line 161) has this:
.entry p {clear:both}
Which tells the paragraph to clear floats. If you were to change that line to
.entry p {
clear: none;
}
then all the paragraphs would wrap around the float. But this may have some unintended consequences on layout on other pages — not sure without experimenting. (You can also just stick the above snippet at the very end of your stylesheet — it will override the earlier specification, and you will then be able to find it easily if you want to remove it.)
That’s as far as I can go without spending a lot of time of this. If you edit your stylesheet, make sure to make a backup first. The safer approach is to comment out the old code (wrap old code with /* […OLD CODE HERE…] */ ) and put your new code underneath, so that you can see what you changed.
It sounds like you are new to CSS. So here’s my advice on learning how to modify and tweak the CSS of your theme:
1) get a decent HTML/CSS editor. There are lots of free ones out there. Personally I like Dreamweaver (expensive), but that’s because I’m used to it and like certain features of the editor. Do NOT use Frontpage. Also, I don’t recommend using the WP-admin panel to directly edit files.
2) backup your whole theme, so that you can experiment without worrying.
3) get a free FTP client (Filezilla recommended) and use that to upload and download files to your server.
4) Get the free Firefox plugin “Web Developer” which has many tools that are useful for testing and analyzing CSS layout and styling.
5) start learning basic CSS. A great place to start is the Westciv complete css guide — the free online tutorials will give you a thorough grounding.
CSS has a bit of a learning curve, esp. with regard to layout (“positioning”), but tweaking an existing theme is a great way to learn as you go.