How To Set A Custom Permalink For Portfolio Posts
To set a custom permalink structure for portfolio posts, go to the "portfolio" tab in theme options and enter your custom slug in the "Portfolio Slug" field. Just make sure its not the same name as your portfolio. So if your portfolio page is called "portfolio", your slug could be "portfolio-items". Once you insert the custom slug, go to "settings > permalinks" and select the "post name" and hit "save changes".