Portfolio custom post type is enabled via X40 Extension. This plugin is distributed with this WordPress theme and must be installed and activates as any WordPress plugins.
The X40 Post Grid widget can be used to display grid of portfolio items. This widget can be used to display other post types also. You should set Post Type to Portfolio in the widgets settings to display portfolio items.
Portfolio items display items navigation on top. This navigation has link to portfolio items list. This list can be created in the Page Builder via X40 Post Grid widget. You should set
Appearance / Customize / Portfolio / Custom Portfolio List in WordPress Administration Panel.