Portfoilio : New item add
You have to start from adding a new tags in component, without them you won't be able to add new items. Add at least one new Tag. The same tag can be applied to many different items across portfolio.
Please follow the link to get detail info:
https://www.joomshaper.com/documentation/joomla-extensions/sp-easyimagegallery#how-to-add-new-items