If you wish to use the Portfolio feature of this theme, simply make sure you have the plugin installed first, then navigate to the Portfolio Menu area of your dashboard.
To change the text that appears at the top of your portfolio archive page, click on Archive Settings.
To add a link to your portfolio to your Navigation menu, go to Appearance > Menus.
Then add a custom link with http://yoururlcom/portfolio
Replace the "yoururl.com" portion with your domain.
Save and TADA!