Upload the folder portfolio to the directory /wp-content/plugins/
Activate the plugin via the 'Plugins' menu in WordPress
Please check if you have the template files 'portfolio.php' and 'portfolio-post.php' in your templates directory. If you can't find these files, then just copy them from the directory '/wp-content/plugins/portfolio/template/' to your templates directory.
Create a page and select a template in the Page Attributes block.
Create (if necessary) Technologies and Executor profiles.
Create portfolio item, add title, description, short description, and upload the images one of which should be set as featured. Publish portfolio then.