By default our custom post type have give slugs, such as portfolio, and it has categories and tags with custom slugs like this: portfolio-category, portfolio-tag. If you need to change these slugs, go to Apperiance >> Theme Options >> Portfolio. And from there change slug to whatever you want. The only thing to remember is that you need to refresh your permalinks to make new slugs work. Go to WordPress Settings >> Permalinks And resave permalinks. Now your custom post slugs work.