To enable users to search help, including help topics, you will need to install the core Search module, configure a search page, and add a search block to the Help page or another administrative page. (A search page is provided automatically, and if you use the core Claro administrative theme, a help search block is shown on the main Help page.) Then users with search permissions, and permission to view help, will be able to search help. See the related topic, @help_search_topic, for step-by-step instructions.