Create portfolio items & portfolio page
To create a portfolio, you need a custom post called "portfolio" or "work" or whatever you like. The advantage of using this theme is that you can create your own custom posts with customisable templates.
To create a custom post, go to Lists - Add New. Here you can set the name and icon for your custom post. The template can be built as a regular page, using Hybrid Composer.
Next, you'll see your newly created post in the left pane. Use it to add your portfolio items. Please note that the template is locked and you'll only be able to add content to your items. To make changes to the layout too, just click the unlock icon on the upper right panel:
Lastly, you'll create a page to showcase all your portfolio items. Create a regular page and use the Grid List or Masonry List element to display your items.
Below is a video showing the full process: