As you might already see the Infinity theme requires a Worpdress custom field to make that Magazine cover style works, as it's very different from 'standard' post entries. The tricky part is that before you publish your post, scroll down to:
Key: thumbnail
Value: path to image
Once you have typed the image path, click on publish, and your latest post can be shown as a thumbnail image (235*150 as default value). In case you wanted to change the cover image, edit your current post, and scroll down to custom field, and change that image path and hit 'update', and everything will be okay.
Twitter stuff
open the left.php file and go line 7, replace the id with your own
<script type="text/javascript" src="http://twitter.com/statuses/user_timeline/yichi.json?callback=twitterCallback2&count=1"></script>
Delicious bookmarks
Open the left.php and go line 24, replace the id (here: yichi) with your own:
<script type="text/javascript" src="http://feeds.delicious.com/v2/js/yichi?count=8&sort=date"></script>
That's it, the theme will work just fine, if you have any question and comments I'll be glad to hearing and help you make it work.