Every category uses a category layout of a template.
To display your fields in frontend category view (*like joomla's category view)
-- Go to your category and check which template it uses, (this is also shown in categories list since v1.5.6)
-- Goto template management and edit the category layout of the template you found above e.g. 'blog'
-- Add your fields in various template positions
NOTE some templates (e.g.) besides template positions also have parameters with which you can enable / disable showing CORE fields , e.g. created by user. These can be edited in every 's category configuration.