To create a global Portfolio page that will show all your portfolio posts go to your dashboard Pages tab>Add new. Type a page title and select Portfolio template in Page attributes
Click Publish button and see your portfolio
If you need some content shown before portfolio items, then add it into Text/Visual editor or use Elementor page builder
Now you can work over portfolio design and options.
Featured image
Set featured image that will be shown on post page
Sidebar Picker
Select desired sidebar area.
