Even if you only have a small amount of money to invest, you can likely get started. Some people start by enrolling in an employer-sponsored retirement plan, like a 401(k). Recent U.S. Department of Labor research indicates 62% of Americans have retirement benefits through work.
Another option is to open an investment account through a bank or investment broker, who can help you buy and sell investments. With this approach, you'll likely have to pay trading and annual fees and other service costs.
Regardless of what option you choose, you'll probably want to do your research to understand each type of investment that you're interested in pursuing, and exactly how you could earn a return on each. It's crucial to note, however, that no investment of any kind can guarantee growth, and may instead lose value over time.