For starting a new article, you may first want to draft the article in a user sandbox named after the topic, such as
User:Stan Lee/Project X,just as you would when expanding an existing article. Work on it until it meets the basics requirements for new articles: it should be based on significant coverage of the topic, in reliable sources that are independent of the topic.
When you are ready to make it live on Wikipedia, try asking an experienced editor you've encountered to look it over and see if it meets the basic requirements for new articles. One way is to submit the article to the Articles for creation project. To do this, copy, paste and save this code at the top of the draft article: {{subst:submit}}
Articles can however, be moved directly to the article mainspace. Click the Move tab, then move it out of your sandbox to its final title. Note that if the page has problems from the perspective of experienced users, it is far more likely that the page will be nominated for deletion if you move it yourself, without having it checked first.