Here's how to show your latest tweets in the theme:
1. Go to your Settings page in Tumblr
2. Select the blog with the theme installed on the right sidebar
3. Scroll down to the "Twitter" section
4. Connect your Twitter account with your Tumblr Account
5. Go back to Tumblr, and click "Customise" on the right
6. On the left, make sure "Show Latest Tweets" is turned on
7. Click "Save"