By default, some of our themes come with a support for Jetpack portfolio, so there is no need to enable it in the Jetpack settings. There are some cases when the theme support is ignored.
In this case, you’ll need to use Jetpack settings: go to Jetpack → Settings → Writing in your WordPress Dashboard and toggle on the Portfolio option under Custom Content Types.
You can add a portfolio item easily by going to Portfolio → Add New in your WordPress Dashboard.
All portfolio items are displayed in an automatically generated portfolio archive page. The portfolio archive page can be found on your site at http://yoursite.com/portfolio/ (replace http://yoursite.com/ with your own site URL).
You can add the portfolio archive to the Custom Menu, using a custom link.