A trademark is a form of intellectual property that consists of a recognisable sign, design, or expression used to identify goods or services as coming from a specific source and set them apart from those offered by other parties. The owner of a trademark may be an individual, a company, or another legal body.
Filing for a trademark in the U.S requires you to file an application with the United States Patent and Trademark Office. Here’s the application page.
Check out this video for more info on filing for a trademark without a lawyer: