Every entity carrying on business in Nigeria must be registered at the Corporate Affairs Commission. Registration may take the form of a business name, or incorporation (limited liability company). Often for reasons of expansion, and because of the many benefits attached to giving the business a separate legal personality, incorporation is preferred. Using the specific circumstance of this question, 'incorporation' is distinct from 'business name'. If I am correct (going by the tone of your question) in saying that High5 Events is a limited liability company, then you would be mistaken to add a business name to it. The proper course would be to incorporate Headline-if necessary-under High5 Events, with High5 Events becoming the parent company, and Headline a subsidiary. If you prefer not to incorporate another company just yet, you could register Headline as a business name and operate it separate from High5 Events, knowing that the business name can be converted to limited liability in future and added under High5.