By default, any templates in this category should be navbox templates (and possibly templates of more uncommon types). It may include one or two infobox templates, otherwise it may include an infobox subcategory named after itself (i.e. if this category is "Name templates", its infobox subcategory would be "Name infobox templates").
To include a template in this category, add <noinclude>[[Template:Template category|{{PAGENAME}}]]</noinclude> to the end of the template code, making sure it starts on the same line as the last character of the code.
Template documentation