I created a portfolio page and would like to assign a post category to display the assigned items. However, my categories are not listed in the list to chose from. The only entry in that list is called “Select category”.
Did you set up the Categories under Posts or Portfolio? They need to be set up as Portfolio Categories, I believe you also need to have at least one portfolio entry assigned to each category (on the right side of the screen when creating / editing a portfolio entry) before the category will show up in the list.